The SGTLS "achievements" system is a special server side plugin which was developed by a SGTLS community member which adds a whole new level of game play by introducing an acquisition/accomplishment system which is dynamic in nature and was specifically created for SGTLS.
Due to being a custom plug-in ran on the server side the "achievements" system won't necessarily be on all the SGTLS server. If you enjoy the added value of the achievement system while playing SGTLS it is recommended that you play only on the servers running it.