Cookies are primarily an American name for a type of biscuit. Large, flat and chewy, often with added flavours like chocolate chips.
The term Cookie actually comes from the Dutch: koekje, diminutive of koek or “cake”.
Biscuits in the USA can be small leavened breads, known as scones in the UK, or small sugary unleavened treats, similar to most of the world.
You may hear the term Oreo Cookie, but even the company who invented them were The American Biscuit Company.