Thank you Esmi and Pedjas!
I'm thinking to create a Real Estate website and I would like each property to have a specific ID and the ID to be a part of the url.
where 1 is the ID of the property.
But the problem is that WordPress is counting an ID for each post, page, custom post and picture.
So, for the first property I could get ID:1, but for the second property I could get ID:8, because I could have 7 pictures uploaded for the first property.
Serious aesthetic problems could occur if I'll have many properties and for the 100th property I could get a very ugly ID - something like 252432.
Well, I'm sure you get the point.
That's why I need a way to have two IDs range: one for the custom posts (properties) and one range can be for everything else.