Pardon my ignorance, but what is a prop firm, I've researched the topic a bit but am at a loss to really grasp the full concept. Do they lend you money - is it a glorified version of margin lending or RegT? Yet, is there some sort of profit sharing involved, and yet also 'training' and a sort of partnership? Say you had a decent amount of funds, 100k+ I can't fully understand what the advantage of prop trading is, any comments welcome.