Operations are simple process we do to numbers to add and multiply and, subtract and divide. A function is a combination of numbers and, operator/operations and, some variables, this has no limit how much number or variable one put inside.
My question is, what is differential and integration classified into? Seems like a process so it's an operation but not just number but other operators also.
Integration and differentiation are both functions of functions. You put in a function, you get out a function. Often functions of functions are called operators as well.
Concerning making up names in maths in general: There is no governing body that decides on how to call things in maths. Names are more fluid and therefore anyone who writes a book or holds a lecture needs to painstakingly define every object they talk about, before working with them.