An option refers to the right but not the obligation, to buy or sell a futures position at a given time.
When standardized, traded options on a futures exchange (eg MATIF, EUREX, CBOT) are refered to as options in the classical sense.
"Warrants" are bearer bonds, that are issued by the issuer (mostly banks). They are traded on stock exchanges on which also shares are traded (eg on the Frankfurt Stock Exchange). Unlike traditional options, in which both the position of the buyer and the seller can be taken, only the position of the buyer can be taken for warrants.
Individually negotiated options between two parties, where the conclusion of the contract takes place outside of a futures exchange, is referred to as "OTC option".