Can anyone tell me what is this and what it does?

Kip, that is reference designator U7930 and it is a Texas Instrument TPS3808G33DBVRG4 in a SOT23-6 package. The description for that is a Programmable-Delay Supervisory Circuit family of microprocessor supervisory circuits monitor system voltages from 0.4V to 5.0V, asserting an open drain RESET signal when the SENSE voltage drops below a preset a logic low. The datasheet for that is available right here. It is a bit hard to come by in a single quantity. Hope this helps, good luck.