Step into: Most likely you will use step into command more than you will use step over command.
When you choose step into, the next line of the code is executed and the program pauses again in break time. If line of code is call to another procedure will be displayed. To continue stepping through your program execution, continue choosing the step into command.
Step over: The step over also executes one line of code at a time. The difference between Step Over and Step Into occurs when your code calls to other procedure. Step over displays only one line of code in the current procedure.