Pointers and manual memory management

int value = 42;
int *ptr = &value;
printf("%d\n", *ptr); // 42, dereferencing the pointer

int *numbers = malloc(5 * sizeof(int));
numbers[0] = 10;
free(numbers); // you are responsible for freeing what you allocate

Every malloc needs exactly one matching free. Forget it, and you leak memory; free it twice, or use it after freeing, and you get undefined behavior — this is the exact category of bug that languages like Rust were designed to eliminate at compile time.