The defining characteristic of pain is the desire for it to end. Pain is discomfort and fear.
There are 3 types of pain.
The first and most basic is physical pain. It is pain felt when the body reacts to stimuli that damage it. It is arguably the most important type of pain because not responding appropriately to it could lead to death. Physical pain can be due to external causes - burns, cuts, hits; or internal - hunger, illness. Physical pain is most associated with discomfort.
The 2nd type is mental pain which is pain caused by contemplation of pain already experienced.
The 3rd is emotional pain. It is caused by anticipation of pain that one expects to suffer. Emotional pain is most associated with fear.
The above classification might seem incomplete since it seems not to allow for things like the pain of heartbreak. However, love can be seen as a way to get physical comfort and/or pleasure. Thus, the end of that love means the thwarting of that expectation or the cessation of that pleasure, then it can be easily classified under emotional pain.
I experience MP & EP in my throat and chest. Both feel clogged. In my chest, I feel as if there is a scaffolding. And something monstrously heavy, like a rusty engine block is falling through it. And it momentarily catches on some of the struts of the scaffolding. It hangs precariously, its weight slowly overpowering the support. And then it falls again with a rending crash. Until it catches again.