I dont understand some english sentences

hi
When i say (I bet she gave him two tight slaps) what does tight slaps mean?

I dont know what is the difference between 2 senteces:

1. The University of Manchester;
2. Manchester University

Mimi,
I think both are correct,because adj must comes before a noun when we don't use a preposition as in the second,but in the first when we use a noun first we must followed by a preposition then an adjective.I am none native speaker ,but I want help you as I learned .