I am relatively new to contesting, and I have heard of a category called SO2R (Single Operator, Two Radios). Are they really talking about 2 radios, or just 2 VFOs in one radio? Running one radio seems to be a full time job, especially with the logging involved. How is the second radio used? What are the advantages over a single radio?
Generally SO2R means one person ("Single Operator") with two separate transceivers attached to two separate antennas ("Two Radios"). The operator doesn't actively transmit and receive on both at the same time, as you say it's a full time job with just one radio.
The second radio (that is, which ever radio is not currently being transmitted on), is typically used to listen on a different band while they are transmitting with the first radio. The only real advantage of this in a contest sense is to score more points. The more people you can hear calling the more you can respond to, and more contacts equals more points.
Also, assuming you aren't actively transmitting, you will be receiving on two separate bands, which increases your chances of hearing someone calling.
I believe you can also call CQ on one radio while search and pouncing on the other. I imagine this takes some level of skill to use effectively.