void Foo(sf::sprite * p_sprite);
Foo(& anotherSprite);

You're becoming confused because C++ reuses the * and the & for different but related things.

Above, the * when used with a type (sf::sprite here) means pointer declaration. So this function takes a pointer argument.

The & when not used with a type (also as above Foo call) means ‘address of’ an object. Since a pointer is just an address, you can use the & to send the address of an object to a function expecting a pointer.

And you've seen that & means Reference declaration when used with a type. 2 different but related uses. Kinda sucks but once you get used to it, it's fine.

To make it even more confusing, you have pointer dereferencing using * ; you can just think of this as ‘the value at’ some pointer.

Honestly, this is a lot to understand in such a short space. Find a good pointer/reference tutorial and go into it knowing that * and & mean different things depending on how/where they are used.

@Josheir That's great.

Originally I was thinking you were passing around pointers to raw image data in your game code. I'm not sure how the SFML Sprite class works but I'm sure it's better to pass those object ref/pointers around game code rather than passing around raw data ref/pointers.