Checks your code for errors.
Stops the serial monitor, or unhighlight other buttons.
Creates a new sketch.
Presents a menu of all the sketches in your sketchbook. Note: due to a bug in Java, this menu doesn't scroll; if you need to open a sketch late in the list, use the File | Sketchbook menu instead.
Saves your sketch.
Uploads your code to the Arduino I/O board. Make sure to save or verify your sketch before uploading it.
Displays serial data being sent from the Arduino board (USB or serial board). Uses the baud rate (serial speed) specified in the Tools | Serial Monitor Baud Rate menu, which must match the baud rate passed to the beginSerial command in your sketch.
Note: the serial monitor currently only supports data coming from the Arduino board to the computer. If you need to send data to the board, you'll need to use another program like HyperTerminal (on Windows) or ZTerm (on the Mac). Or you can talk to the board from Processing, Flash, MaxMSP, etc.
Some preferences can be set in the preferences dialog (found under the Arduino menu on the Mac, or File on Windows and Linux). The rest can be found in the preferences.txt file. The location of this file is displayed at the bottom of the preferences dialog. Edit it only when Arduino's not running (or your changes will be overwritten when Arduino exits).
Checks your sketch for errors.
Uses a library in your sketch. Works by adding #includes for the library header files. This signals the Arduino IDE to link those libraries against your sketch when verifying and uploading. This makes extra functionality available to your sketch, but increases its size. To stop using a library, delete the appropriate #includes from the top of your sketch.
This formats your code nicely: i.e. indents it so that opening and closing curly braces line up, and that the statements instead curly braces are indented more.
This menu contains all the serial devices (real or virtual) on your machine. It should automatically refresh every time you open the top-level tools menu.
Before uploading your sketch, you need to select the item from this menu that represents your Arduino board. On the Mac, this is probably something like /dev/tty.usbserial-1B1 (for a USB board), or /dev/tty.USA19QW1b1P1.1 (for a serial board connected with a Keyspan USB-to-Serial adapter). On Windows, it's probably COM1 or COM2 (for a serial board) or COM4, COM5, COM7, or higher (for a USB board) - to find out, you look for USB serial device in the ports section of the Windows Device Manager.
This menu item controls the baud rate (speed) that the serial monitor uses to communicate with a sketch running on the Arduino board. It must match the value passed to in the code of the sketch.
This baud rate does not affect the process of uploading sketches to the Arduino board. That depends on the serial.download_rate variable in the preferences.txt file (see the FAQ for more details).
This burns the bootloader to your Arduino board, using an an AVR-ISP connected to the serial port selected in the Serial Port submenu. For more details see the bootloader page.
Windows and Linux only'. Burns the bootloader to your Arduino board, using a parallel programmer.