I saw on the microsoft homepage that there are 2 types of license for the sql server, first is processor license and the second is server + cal.

What is the diference between those two types of license? What for can you use them?

Best regards.

One license you pay for the processor speed. The other you pay based on the number of connections allowed at a time.

Depending on the prices and your design you choose accordingly. For a web app you may have only 1-5 connections so a cal license may be cheaper. For an internal application you may have 200 possible connections at a time so a server based license may be cheaper.