Dirty VS Impure

This looks it is hard to understand for any non-Muslim.
There are two type of the "Dirty" we deal with here in Islam
The first type is the Dirty, means the items that are obviously not clean, due to dust for example, or to surfaces that are not clean, so those are kind of fine to do most of practice with it.
Off course, it should be clean, but being it unclean will not prevent the practice.

While the other part is "Impure" or "Najis" = ???
This is the part that any Muslim practice should worry about.
So, if a surface have seen some "Urine" for example, it considered "Impure" and cannot do Pray with it for example.
Same goes to poops, semen, and the most important one, DOGs
It was kind of tough to make people understand why we don't want to touch dogs, they are clean and cute, but Islam consider dogs as Impure animals, meaning we have to wash before we do any practice.
Same goes to dog's hair, so if there is a dog in the house, I cannot practice my prayer there, sorry dogs
While Cats are not Impure, fish, Birds, etc. Dogs are the tough part.