Land tax or property tax

Do we need land or property taxation? Any exemptions? Local or central tax?
There are different systems in different countries. However, mostly the real property is possible to buy and sell. Why at all tax real property? Why we need (or do we need) taxes at all.
Maybe we'll find people from different parts of world to discuss over these issues and go deeper into something.
Of myself - one of the persons behind Estonian land tax system and thus knowing a lot of it - why we did what and which consequences. Btw, I do not think that our system was the best, even, not thinking that current scheme is what we initially wanted. But let's go into details later, during or through discussions.