What are references in C++? Why do you need them when you have pointers?

A reference variable is actually just a pointer that reduces syntactical clumsiness related with
pointers in C (reference variables are internally implemented as a pointer; it’s just that programmers
can't use it the way they use pointers).
As a side note, a reference must refer to some object at all times, but a pointer can point to NULL.
In this way, references can be more efficient when you know that you'll always have an object to
point to, because you don't have to check against NULL:
void func(MyClass &obj) {
obj.Foo();
}
Is better than:
void func(MyClass *obj) {
if (obj) obj->Foo();
}