Microsoft® SQL Server® 2012 Service Pack 2 (SP2) Express
As you said in comments you'd like a SQL Server + a SSMS.
I would suggest not using a SQL2012, but going for a more recent version.

Using this this link you can download the SQL Server itself.
The 2 free versions are express and Developer. More information about the differences between versions can be found here : SQL Editions and SQL Pricing


Developer you should use if you're just trying to develop some things at home, NOT COMMERCIALLY. It has all the features enterprise has.
Express will give you a basic sql server with some limitations.


Afterwards you can get SSMS using this link.
SSMS is free, and its just used to work on your SQL Server