What are the major differences between mysql5.6 and mysql 5.7
The release notes for MySQL 5.7 are here.

"What's new in MySQL 5.7" can be found here.

Changes of note:


ONLY_FULL_GROUP_BY is now turned on by default, meaning MySQL
will no longer return random data when a user has incorrectly
specified columns in the where clause, but missed them out of the
group by clause.
Improvements to online DDL - more ALTER operations can be done
online without the storage engine having to make a copy of the object
in question.
InnoDB now supports MySQL-supported spatial data types
InnoDB supports tablespaces
Native JSON support
A new sys schema, with summarized performance data 
Multi-source replication