This is a Benzene Ring. It is a ring of 6 Carbon atoms.

This is a Phenol.
The "-OH" stuck on the Benzene Ring is Oxygen + Hydrogen. It is called a Hydroxyl Group. There can be one or several on a phenol.

This is Norepinephrine. It is a neurotransmitter. Notice the Hydroxyl Groups. (HO is the same as OH) It is phenolic.

This is Salicylic Acid. It is the basis for the salicylate chemicals including aspirin. It, too, is phenolic