Riba means Interest. Riba is Haram (forbidden) in Islam, and it is considered a major sin.
Riba (Arabic: ربا, [rɪbæː]) means Interest. Riba is forbidden in Islamic economic jurisprudence fiqh and considered as a major sin. Simply, unjust gains in trade or business, generally through exploitation.
There are two types of riba discussed by Islamic jurists: an increase in capital without any services provided and risktaking, which is prohibited by the Qur'an, and commodity exchanges in unequal quantities, prohibited in the Sunnah.