How many different ways can you join one set of wires to another? Check out the items on this page and I'll bet you find more ways than you thought!
Remember, a connector goes on the end of an unterminated wire or is built-in to equipment.
An adapter connects two or more connectors. The connectors can be of different styles and sexes. But the adapter does not change the signal characteristics in any meaningful way. Adapters are passive devices. A phone line adapter might "Y" the phone line to two devices, or reconfigure line 1 and line 2 in the jacks. But the signals themselves are not changed.
A converter does all that an adapter does, but it also changes the signal characteristics. For instance, a DSL splitter has outputs that are modified versions of the input, and are not interchangeable.