Let's say person A has patented a machine that converts apples into oranges. Can person B go ahead and make use of this patent and start mass producing the machine while crediting A for his idea?
A patent gives the owner an exclusive right to forbid others to make, use, sell, import or export the claimed invention. Anybody else has to get the owners permission (license) or can be sued.
Note: the owner themself might be impeded from using their invention due to other patents forbidding a part or all of it.
In the US and most other countries (I think I heard India is an exception) not using a patent does not take away any of those rights to forbid the usage.
And it's always forbidden implicitly unless explicitly allowed.