Barre-Chord question

Hi all, i have only been playing guitar for about 3 months but its not too much trouble since i've had piano for 5 years.

Actually i was wondering if someone could explain teh theory behind barre-chords. If i play an Amaj7 chord shape at the 8th fret what kind of chord have i jsut made? is it still an Amaj7 or another maj7 th chord or what?

Im sorry i dont know how else to phrase the question. If there is anything that isnt understood pls tell me.

Thank you :)

http://www.guitartricks.com/lesson.php?input=8283&s_id=76

just count up chromatically from the root note.

Example: An A played at the 7th fret is an E

Open = A,
1st fret barred = A#
2nd fret barred = B
3rd fret barred = C
4th fret barred = C#
5th fret barred = D
6th fret Barred = D#
7th fret Barred = E