Heterosexuality is being sexually attracted to or aroused by people of the opposite gender - usually the basis of a sexual relation between a male and a female. The opposite is homosexuality (male-male, gay, or female-female, lesbian). There also exist other variations, such as bisexuality, which encompasses both, or asexuality, which encompasses none.
Heterosexual erotica and pornography comes in two kinds: first, material that is not specifically heterosexual, for example, erotic depictions of a male or female model (which are usually attractive for heterosexuals of the opposite gender, but may also be attractive to homosexuals of the same gender); second, material that portrays heterosexual erotic attraction and activities.
Heterosexual erotica and porn can depict partners of approximately the same age or of different age. Especially in completely fictitious non-photographic media such as drawings and comics it is popular to show youths; either two minor characters or a minor and an adult.
Heterosexuals, spanking and BDSM
Consensual spanking and BDSM is equally found in heterosexual and homosexual partnerships. Both pairings, F/M and M/F, are very common. But heterosexuals also often like to watch same-sex spanking or BDSM play, especially that of the opposite gender (e.g. men like to watch F/F scenes).
In professional BDSM and spanking services, there seems to be a much greater market for female dominants than for male ones. female submissives are also typically much more sought after than male submissives.