Updated intro sentence

Author: JeffSchering

source/install/install-rhel-66-mysql.rst

@@ -3,7 +3,7 @@
 Installing MySQL Database Server
 ================================
 
-You can install either MySQL or PostgreSQL. To install PostgreSQL, see :ref:`install-rhel-66-postgresql`
+Install and set up the database for use by the Mattermost server. You can install either MySQL or PostgreSQL. To install PostgreSQL, see :ref:`install-rhel-66-postgresql`
 
 **To install MySQL 5.7 on RHEL 6.6:**
 

source/install/install-rhel-71-mysql.rst

@@ -3,7 +3,7 @@
 Installing MySQL Database Server
 ================================
 
-You can install either MySQL or PostgreSQL. To install PostgreSQL, see :ref:`install-rhel-71-postgresql`
+Install and set up the database for use by the Mattermost server. You can install either MySQL or PostgreSQL. To install PostgreSQL, see :ref:`install-rhel-71-postgresql`
 
 **To install MySQL 5.7 on RHEL 7.1:**
 

source/install/install-ubuntu-1604-postgresql.rst

@@ -3,7 +3,7 @@
 Installing PostgreSQL Database Server
 =====================================
 
-You can install either PostgreSQL or MySQL. To install MySQL, see :ref:`install-ubuntu-1604-mysql`
+Install and set up the database for use by the Mattermost server. You can install either PostgreSQL or MySQL. To install MySQL, see :ref:`install-ubuntu-1604-mysql`
 
 Assume that the IP address of this server is 10.10.10.1