In C++, what is the use of template parameter when it doesn't appear in the following class or function declaration?

Many times I see these types of codes.
What is the use of template in the code below?
I ask this because the template parameter T does not appear in the declaration.

template <typename T>
struct op_pointer_to_mat;
template <typename T>
struct op_pointer_to_col_vect;

Does it mean that the definition of op_poineter_to_mat and op_pointer_to_col_vect is somewhere else with template parameter T?