IDE stands for Integrated Development Environment. Simply put, the IDE is a computer program which makes it easy to create, edit, and upload software for Arduino. It detects mistakes and tells where they are.
In the Arduino software, libraries are present to make programming life a little more easy. Libraries are fantastic help to get up and running very fast, or test components and circuits you connect to the Arduino. Libraries can be found under File > Examples. Also, you can get to know how to write code if you didn’t know that already.
Make sure you select the correct Arduino board in the menu under Tools > Board and set the serial port to the correct address (Tools > Serial Port).
Baud rate is the signalling speed of the interface. Simply put: it reads with a certain speed. If you deliver data at the same speed, the data can be read. If the baud rate differs, data can not be read and errors will be the result.
The serial monitor, is a very useful tool in debugging.
You can output values of variables visible on the screen. You can do this before and after you change the value of a variable, before and after if loops (to check if a program actually runs the code inside an if loop) or to check the value of an analog input connected to a sensor. Also, text can be added, so you are still able to make sense of the numbers that are on the screen.
Serial.print(“Hello World! The value of Variable is: “); gives you: “Hello World! The value of Variable is: ”
Serial.print(variable); gives you the value of the variable
Serial.print(“\n”); gives you an Enter between two lines
More examples can be found on http://arduino.cc/en/serial/print
Also have a look at the Serial Plotter which can be used to plot variables printed to the serial port in real time on the screen.