There are probably thousands of different definitions of the word "Christian."
For a simple easy definition:
A "Christian" is anyone who not only follows the teaching of Jesus Christ but also seriously, devoutly, and prayerfully accepts Jesus Christ as their Lord and Savior.
The usually accepted main Branches of Christianity are:
A few of the denominations within the branches are:
African indigenous sects (AICs)
Latter Day Saints
Stone-Campbell ("Restoration Movement")
New Thought (Unity, Christian Science, etc.)
Brethren (incl. Plymouth)