As you know the code within braces is known as block of code and there will be times when you want your block of code to be repeated multiple time. In general the code executes only once and sequentially so if you want it execute multiple times then either you have to write it multiple times or use the idea of Loops.
In your programming you are going to need or build expressions which will help you in your calculation. For example you calculate average of some number, for that purpose you are going to build expression. Expressions are built with operators and operands. Operators are symbols or functions that tells compiler to perform specific mathematical or logical operations and operands are something on which operators work.