When should I use a pointer instead of a regular variable?

A simple way to think about it is that a variable is the contents of a house, while a pointer is the house’s address. In C, x means the value stored in x, &x means the address of x, and *p means the value found at the address stored in p. If a function receives a pointer to x and writes through it, the original x changes; if it receives x by value, only a temporary copy changes.

Pointers are also useful for dynamically allocated data, large objects, and data structures such as linked lists, trees, stacks, and queues. Instead of moving the whole object around, you can pass a small address that refers to it. They also let multiple parts of a program share one object.

Pointers expose how memory is represented underneath the language. They’re needed in C when manually managing memory or working with heap allocations, and they’re useful when an object may not exist yet or when data is arranged in separate places in memory. They aren’t automatically better, though—if a copy is small and you don’t want shared mutable state, passing a value or returning a modified copy can be clearer and safer.

The biggest difference is copying versus referring to the original data. Passing a normal value to a function usually gives the function its own copy. Passing a pointer gives it an address, so it can work with the same memory as the caller. That matters when the function needs to modify the original variable or when copying the value would be expensive.