when do I need to put in curly brackets?

Answer 1

When there is more then one statement in the if-else. You can skip the { } when there is just one statement, but it is recommended to always put the brackets. It makes the code more readable.

Answer 2

You put in curly brackets every time you start a new method and you close every time you end the method. The same applies when you start and end a class, a loop, a condition. Curly brackets are how you know that the code separated.

Answer 3

it is the seperator for that particular sequence