What is mean inline function

Answer 1

Inline functions are functions that are put in the code a bit differently. Usually the code for a function is put separate from the the code that is calling it. The code of a inline function is inserted at the place where it's called.
This is supposed to be faster as no call and return statements have to be executed. Still, the additional code might lead to longer loading time.

Answer 2

The compiler replace the function call with the corresponding function code