Xlock locks the x server till the user enters his/her password at the keyboard. while xlock is running, all new server connections are refused. the mouse cursor is turned off. the screen is blanked and a changing pattern is put on the screen. if a key or a mouse button is pressed then the user is prompted for the password of the user who started xlock.
this version is built with graphical modes. the companion package xlockmore does not contain them. this is the only difference between the two packages.