It gets the ID of whatever button your are holding down; usually, you put it in a variable so that you can do 'if' statements with it. For example:
B=BUTTON()
If B==1 Then 'Up
' Do whatever
ENDIF
Here's how your supposed to use it
B=BUTTON()
IF B AND #UP THEN PRINT "^"
IF B AND #DOWN THEN PRINT "v"
IF B AND #LEFT THEN PRINT "<"
IF B AND #RIGHT THEN PRINT ">"
IF B AND #A THEN PRINT "A"
.......
IF B AND #L THEN PRINT "L"
(it contains every button's data in one number)
Ignore Feature ID and Terminal ID
Thats for advanced multiplayer stuff
You use buttons like this:
IF BUTTON((Put 1, 2, 3, or 4 in here)) AND #(put button name, e.g. A, B, X, Y) THEN (put what you want the button to do here)
It should look like this:
IF BUTTON(2) AND #A THEN PRINT "It works!"