The TCI is a measure of the similarity between two people's taste in films. The lower the TCI, the greater the tendency to agree on which movies ruled and which sucked.
Once you've ranked a handful of movies at Criticker, you can generate TCIs with everyone in the community -- both normal users and published critics. It's better than just finding a few people with whom you generally agree -- Criticker will show you the exact people whose tastes are the most similar to your own. It's scientific (kind of)!