Different species compete. (Between species)
This is competition between individuals of different species. For example sheep and rabbits compete for the grass in a field.
Another way to help you remember what interspecific competition is:
Interspecific contains er in the middle of it, as does ‘different’
So inter specific competition is different species in competition.
Rabbits and sheep engage in interspecific competition for grass within a field.
In a forest there’s interspecific competition between tree species. Some tree species will grow faster and taller than others. They will then shade the other species, reducing the amount of light that is available to them.