Asexuality is an umbrella term of a sexual orientation where an individual experience little to no sexual attraction. Asexuality can be both an identity and orientation. Asexuality is a spectrum and people who identify as asexual can fall anywhere on the spectrum. Sexual attraction has a different definition for different people. Some of the terms used by people who are asexual include demi-sexual, grey-A, among others.
People who experience no sexual attraction at all can call themselves ace. Folks can be asexual even if have indulged in sexual activities or are in a romantic relationship.