Hi, Im not sure if this is asked before but what is the difference between basic and gross salary?

For example (numbers are made up):

Gross monthly salary: 2000
"Your gross monthly salary is made up of 50% basic salary, 10% MVC, 9% NPC, 31% NPVP."

So what is my basic salary?

If my gross is made up of half of my basic salary, where is my other half? Why is it not made up of 100% of my basic salary?