There are a couple (OK, maybe more) judgements.
1. Whether one will get into heaven (whether one will have eternal life). Belief in Jesus gets one into heaven (gives one eternal life). This is according to John 3:16 (and elsewhere).
John 3:16 (NIV) 16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.
2. Judgement of Believers’ Works – Once in heaven (once that decision has been made), believers will be judged against their works. Also, the rewards will not be the same for all believers.
2 Corinthians 5:10 (NIV) 10 For we must all appear before the judgment seat of Christ, so that each of us may receive what is due us for the things done while in the body, whether good or bad.
Believers will not be judged for sin at the judgment seat of Christ. Every sin of every believer was judged at the Cross, when God “made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him” (2 Cor. 5:21)
If one checks Bible commentaries (or Googles) for Judgement of Believers’ Works, there is much more information.