What does dublin 1, dublin 2, ect. mean?

Question

im looking at hotels in dublin and it say dublin 1 for some and like dublin 4 for others.

Answer 1

Postal districts. The odd numbers are north of the river Liffey and the even numbers south of the river. Dublin 4 is the Embassy belt, very posh in places, and hotel rates would reflect this.

Answer 2

They are the areas of Dublin, as already stated odd numbers 1,3,5 etc are on the north side of the Liffey, and even numbers 2,4,6 etc are on the southside.  

Also, the lower the number the nearer it is to the city centre.

Answer 3

they are postal districts (like postcodes). for the mail to be delivered.

Dublin is divided by the river liffey. all the odd numbers (Dublin 1, Dublin 3 etc.) are on the north side of the liffey, while the even numbers (Dublin 2, Dublin 4 etc.) are all on the south side of the liffey.

the south side is the posh side (so hotels would be dearer) and the north side is not so posh.