Hi there

I am a little bit confused about modular arithmetic. I don't quite understand what it really means when one number is logically equivalent to another. For example in my book it says:

7 ≡ 2 (mod 5)

what is it about 7 that makes it logically equivalent to 2 (mod 5)? I also believe the book says that 18 is logically equivalent to 3. Does that perhaps mean that 18 is divisible by 3?

In my book it also says that:

h(064212848) = 037149212 mod 111 = 14 , but I don't see how this can be correct. I mean, I am sure the book is correct, I just don't understand why hehe. I really hope someone can help me. Thank you!