Understanding full-text searches
If you are looking up names or looking for simple strings, you are usually querying the entire content of a field. With a full-text search, this is different. The purpose of the full-text search is to look for words or groups of words that can be found in a text. Therefore, a full-text search is more of a contains operation, as you are basically never looking for an exact string.
In PostgreSQL, a full-text search can be done using GIN indexes. The idea is to dissect a text, extract valuable lexeme (preprocessed tokens of words) strings, and index those elements rather than the underlying text. To make your search even more successful, those words are preprocessed.
Here is an example:
test=# SELECT to_tsvector('english','A car,
I want a car. I would not even mind having many cars');
...