diff --git a/app/models/age_range.rb b/app/models/age_range.rb
index 31e8738ff..64df20ed6 100644
--- a/app/models/age_range.rb
+++ b/app/models/age_range.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-# AgeRange is an optional filter used to categorize Events
+# AgeRange
 class AgeRange < ApplicationRecord
   extend FriendlyId
   friendly_id :name, use: :slugged
diff --git a/app/models/statistic_custom_aggregation.rb b/app/models/statistic_custom_aggregation.rb
index 09bc623de..4c6f45087 100644
--- a/app/models/statistic_custom_aggregation.rb
+++ b/app/models/statistic_custom_aggregation.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # StatisticCustomAggregation is an ElasticSearch aggregation that will run when the end-user is browsing the statistics
-# page for the related statisticType.
+# page for the related StatisticType.
 # See https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations.html
 class StatisticCustomAggregation < ApplicationRecord
   belongs_to :statistic_type
diff --git a/app/models/tag.rb b/app/models/tag.rb
index 1fc6a82fe..89a6f6957 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+
+# Tag is a way to restrict an Availability for reservation to users with the same Tag.
 class Tag < ApplicationRecord
   has_many :user_tags, dependent: :destroy
   has_many :users, through: :user_tags
diff --git a/app/models/theme.rb b/app/models/theme.rb
index ca70f8568..c4813a1a4 100644
--- a/app/models/theme.rb
+++ b/app/models/theme.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+
+# Theme is an optional filter used to categorize Projects
 class Theme < ApplicationRecord
   has_and_belongs_to_many :projects, join_table: :projects_themes
   validates :name, presence: true, length: { maximum: 80 }
diff --git a/app/models/ticket.rb b/app/models/ticket.rb
index 5351e9804..2da7fa2a0 100644
--- a/app/models/ticket.rb
+++ b/app/models/ticket.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+
+# Ticket is an reservation of a member for an Event, with a specific PriceCategory
+# For example, Member John Smith smith has book 2 places on Event "Arduino initiation" at price "reduces fare"
 class Ticket < ApplicationRecord
   belongs_to :reservation
   belongs_to :event_price_category
diff --git a/app/models/training.rb b/app/models/training.rb
index 8bf724d4f..abb7a2c95 100644
--- a/app/models/training.rb
+++ b/app/models/training.rb
@@ -1,3 +1,8 @@
+# frozen_string_literal: true
+
+# Training is a course for members to acquire knowledge on a specific matter.
+# Trainings are designed to be scheduled periodically through Availabilities.
+# A Training can be a prerequisite before members can book a Machine.
 class Training < ApplicationRecord
   extend FriendlyId
   friendly_id :name, use: :slugged
diff --git a/app/models/training_image.rb b/app/models/training_image.rb
index f8b5909e0..f06397812 100644
--- a/app/models/training_image.rb
+++ b/app/models/training_image.rb
@@ -1,4 +1,6 @@
+# frozen_string_literal: true
 
+# TrainingImage is the main picture for a Training
 class TrainingImage < Asset
   mount_uploader :attachment, TrainingImageUploader
 end
\ No newline at end of file
diff --git a/app/models/trainings_availability.rb b/app/models/trainings_availability.rb
index fd648465f..3ccab5bd9 100644
--- a/app/models/trainings_availability.rb
+++ b/app/models/trainings_availability.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+
+# TrainingsAvailability is the relation table between a Training and an Availability.
+# Is is used to schedule a training session, for members to be able to book it.
 class TrainingsAvailability < ApplicationRecord
   belongs_to :training
   belongs_to :availability
diff --git a/app/models/trainings_pricing.rb b/app/models/trainings_pricing.rb
index 14e1146aa..689f8946e 100644
--- a/app/models/trainings_pricing.rb
+++ b/app/models/trainings_pricing.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+
+# TrainingsPricing configures the price of a Training session, per Group
 class TrainingsPricing < ApplicationRecord
   belongs_to :training
   belongs_to :group
diff --git a/app/models/user.rb b/app/models/user.rb
index 9be7b4efb..175ab6fc3 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # User is a physical or moral person with its authentication parameters
-# It is linked to the Profile model with hold informations about this person (like address, name, etc.)
+# It is linked to the Profile model with hold information about this person (like address, name, etc.)
 class User < ApplicationRecord
   include NotifyWith::NotificationReceiver
   include NotifyWith::NotificationAttachedObject
diff --git a/app/models/user_avatar.rb b/app/models/user_avatar.rb
index 0e172a01c..15e878841 100644
--- a/app/models/user_avatar.rb
+++ b/app/models/user_avatar.rb
@@ -1,3 +1,6 @@
+# frozen_string_literal: true
+
+# UserAvatar is the profile picture for an User
 class UserAvatar < Asset
   include ImageValidatorConcern
   mount_uploader :attachment, ProfilImageUploader
diff --git a/app/models/user_tag.rb b/app/models/user_tag.rb
index cc2ef37c8..2740753ec 100644
--- a/app/models/user_tag.rb
+++ b/app/models/user_tag.rb
@@ -1,3 +1,7 @@
+# frozen_string_literal: true
+
+# UserTag is the relation table between a Tag and an User.
+# Users with Tags, can book Availabilities associated with the same Tags.
 class UserTag < ApplicationRecord
   belongs_to :user
   belongs_to :tag
diff --git a/app/models/users_credit.rb b/app/models/users_credit.rb
index f1b804dbb..17a6019b9 100644
--- a/app/models/users_credit.rb
+++ b/app/models/users_credit.rb
@@ -1,7 +1,11 @@
+# frozen_string_literal: true
+
+# UserCredit is the relation table between a Credit and an User.
+# It saves the consumed credits only
 class UsersCredit < ApplicationRecord
   belongs_to :user
   belongs_to :credit
 
-  belongs_to :training_credit, ->{ where('credits.creditable_type = ?', 'Training') }, foreign_key: 'credit_id', class_name: 'Credit'
-  belongs_to :machine_credit, ->{ where('credits.creditable_type = ?', 'Machine') }, foreign_key: 'credit_id', class_name: 'Credit'
+  belongs_to :training_credit, -> { where('credits.creditable_type = ?', 'Training') }, foreign_key: 'credit_id', class_name: 'Credit'
+  belongs_to :machine_credit, -> { where('credits.creditable_type = ?', 'Machine') }, foreign_key: 'credit_id', class_name: 'Credit'
 end