SQL SP1 , SP2 , CTP3, CTP4

All,I have to download trail version (express version) in my laptop.OS : Windows 7I have downloaded SQL.EXE. wHEN I try to install sql.exe, it prompted to install SP1. When I search on Google , I can see SP1 with CTP4 , CTP3. To work on SQL 2012, SSIS 2012, SSAS 2012, SSRS 2012 which SP needs to be installed in my laptop.CTP stands for ?CTP3 , CTP 4 ...confusing really...