Universalism is the idea that, through Christ
, all, in the end will be saved. Univeralists believe that hell
is only a temporary punishment
, after which, everyone gets to live eternally happily.
This belief at first seems to conflict with just about everything ever said in the Bible. However, the Universalist belief system rests on the idea that the word which is normally translated as 'eternal' in the New Testament, that is the Greek word aionos, actually means 'long-lasting.' Apparently, the few contemporary sources we have written in the Koine Greek of the time use the word this way. Also, using aionos to mean of finite duration seems to clear up apparent inconsistencies in the Bible itself, such as when Jude calls the fires that destroyed Sodom 'eternal' (aionos). (On a related note, there is a similar word, 'olawm', in Hebrew.)
Outside of their belief in the salvation of all humanity (and some, of all aware beings), Universalists vary greatly in their strain of Christianity. Some are Arminians, and some Calvanists. Some are premillennialists and some amillenialists. They are united only by theire belief in the salvation of all.
This is quite a simplified overview of Universalism. There are many bible passages used to support it as well as many used to discredit it. There are other words thought to be badly translated, and some of the 'revised' translations have problems of their own.