Step 1: List the types of marriage:
Ancient Indian texts (e.g. Manusmriti) describe eight forms of marriage: Brahma, Daiva, Arsha, Prajapatya (the four approved forms), and Gandharva, Asura, Rakshasa, Paishacha (less approved/irregular forms).
Step 2: Define exogamy:
Exogamy (bahirvivah) is the social rule requiring marriage OUTSIDE one's own defined kin group -- such as outside one's gotra (clan) or pravara -- to prevent marriage among close relatives.
Final Answer:
\[ \boxed{\text{Eight traditional marriage types; Exogamy = marriage outside one's own gotra/clan}} \]