The Start block marks the beginning of a programming block sequence in your program. Your program can have more than one sequence. All sequences with a Start block will start automatically when a program is run, and the sequences will run at the same time.
If your robot is turned on and connected to your computer (by USB, Bluetooth, or Wi-Fi), you can also click on the green arrow on the Start block to immediately run that single sequence in your program.

＊If a sequence of programming blocks does not start with a Start block, the blocks will not run.
＊Clicking on the green arrow on the Start block will compile and download the entire program to your EV3, but only the selected sequence will run.