MS SQL Server 2014 is free downloadable software, available on Microsoft official website. Anyone can download SQL Server 2014 free, this is express edition which is suitable for learning and small scale projects. Microsoft has done major changes in SQL Server database engine and added new features to improve query performance in SQL Server 2014.
It comes with different editions to support from small scale business to large enterprise.
SQL Server Enterprise Edition
Ideally suited for large enterprise business, business where down time is very minimum. It come with all top features to support HA (High Availability) for building DR under software assurance.
SQL Server Standard Edition
Less features compare to enterprise but it can be used in medium size business where advance features is not an requirement.
SQL Server Developer Edition
This edition has same features as compare to enterprise, this is used by developer to build the solution and test. Only difference is in license, it is based single user, can not used as production but can be upgraded to enterprise without re-installation.
SQL Server Express Edition
It is free downloadable software. you can use for learning and demos with limited features. It supports only 1 CPU and 1 GB RAM, database size can grow up to 10 GB.
Download SQL Server express edition using below link