Difference between & and std::add_lvalue_reference

Question

while reading some SO questions regarding c++ templates and generally code I did not write I came across using such construct:

template<class T>
std::add_lvalue_reference_t<T> my_foo(T &t) { /*do some stuff and return*/ }

On the other hand I have been always using something like this:

template<class T>
T &my_foo(T &t) { /*do some stuff and return*/ }

And so I have a few questions:

1. Are these snippets of code equivalent?
2. If not, what is the difference between them?
3. If not, which is to be prefered?