Standard base M/V bulbs vs. Mogul bases

Standard vs. Mogul is a reference to the size of the socket it accomodates, specifically the diameter. Standard is what most people would think of as a normal socket diameter, whereas Mogul is much larger. You can't screw a Mogul bulb into a standard socket, or vice versa. If you have an independent ballast unit though, you should be able to connect it to either type of socket and run things just fine. You would just need to buy a Mogul socket, and then connect run some wires out of the socket leads and connect it to the ballast. Mogul sockets are pretty cheap, $5-10, so it really isn't much of an investment.

If you're running a 175 watt setup, you could probably buy bulbs that accomodate either standard or Mogul. If you want to go larger (250, 400, 1000), then you're pretty much stuck with Mogul.