Terpenes and terpenoids are both compounds present in cannabis. These compounds are why cannabis plants have diverse aromas and flavours. Both terms are used interchangeably, but they do have slight differences.
Terpenes are organic hydrocarbons, while there are additional atoms in terpenoids. The atoms are the result of oxidation, which happens when drying and curing cannabis. As such, you can distinguish terpenes and terpenoids as wet and dried out, respectively.