a carbohydrate refers to a molecule made up of a chain of carbon atoms bonded with hydrogen atoms (if I remember correctly from Organic Chemistry).

There are plenty of different molecules, such as Sucrose, Glucose, etc, which are all forms of carbohydrate molecules.

But when people refer to "carbs", they're not referring to the chemical molecule, but most likely processed carbohydrates such as bread.

Hopefully that's more clear