What is the use of static keyword in the creation of a fuction?

#1

I want to know how will we know that this function requires a static keyword or not I mean what is the difference in the functions with and without static keyword and how would we know where to use it?

#2

Use the static variable for the property that is common to all objects. For example, in class Student, all students shares the same college name. Use static methods for changing static variables.