I think that a player is the person who dates several people at one time for certain perks. He/she is 'playing' the other individuals by making them think that this is a committed relationship and getting money, sex, gifts, privileges, etc. in return for the committment.
This person is hard to reform, but it can be done. However, this person is an opportunist. So, even in a relationship, he/she might see an opportunity that needs to be seized.
Dating, on the other hand, is just going out with people in hopes of getting to know them better. This can be done with several people at one time. I'm not talking about sex. I just mean going to the movies, the park, out to eat, etc. If feelings get serious, you can discuss being exclusive. If you have sex before that conversation and get attached, you played yourself.