activesheet in excel VBA

Appologies for wery simple question i have, i'm just new
in programming. Is the Activesheet in excel VBA means that if you have a code

Sheets("Point
            Assignments").Select
lastrow = ActiveSheet.Cells(Rows.Count,
            1).End(xlUp).Row
Range("B2:B" &
            lastrow).Select

Application.CutCopyMode =
            False
Selection.Copy

The
ActiveSheet will be the "Point
Assignments"

Also, in the lastrow =
ActiveSheet.Cells(Rows.Count, 1).End(xlUp).Row what is meant by .END(xlup). Row

Thanks very much for the
help

Regards,
Kenneth