what is index property

[adi5402]

Can some one explain me the properties u can set to colums in a sql database what does
primary - i think i know
Index mean - can some one explain
unique - prob means unique
FullText - can some one explain this

i have set a column of mine to index and now its trowing error all over the place and not letting me do anything in the database it keeps throwung error that column subject is not valid and ideas what could have gone wrong.

its set under the index property and i cant delete it

[Mordecai]

There is a forum for database questions. In fact, it's called, "Database." Your question would be best suited for that environment.

Primary: This is used to keep an ID for each row. You can set something to be a primary key, and autoincrement it.
Index: Used to index the rows.
Unique: Yep, you guessed it.
FullText: Used for full text searching.