A pointer is a variable in C language that stores the memory address of another variable as its value. Pointers are used to manipulate the data in the computers memory, which can reduce the code and improve performance. Pointers can be used to store the memory address of other variables, functions, or even other pointers. The use of pointers allows low-level memory access, dynamic memory allocation, and many other functionalities in C.

To use pointers, there are three steps: pointer declaration, pointer initialization, and dereferencing. In pointer declaration, we only declare the pointer but do not initialize it. To declare a pointer, we use the ( * ) dereference operator before its name. In pointer initialization, we assign the address of a variable to a pointer. Finally, in dereferencing, we access the value at the address available in the pointer variable by using the unary operator * that returns the value of the variable located at the address specified by its operand.

Pointers are especially important in C because they allow us to manipulate the data in the computers memory. They are used for various functionalities in C, such as passing arguments by reference, accessing array elements, returning multiple values from a function, dynamic memory allocation, implementing data structures, and in system-level programming where memory addresses are useful.