'Baseline' is the name of an algorithm (a mathematical process) used to compress (make smaller in file size) a jpeg picture. Apparently, it is the most common form of image compression. See more information HERE
Matrix metering mode
"The metering system in a digital camera is the system which measures the amount of light (EV value, exposure value) in the current frame and calculates the best-fit (depending on metering mode - below) exposure."
Matrix metering mode:
"This is probably the most complex metering mode, and each manufacturers exact detail on how they implement matrix metering is closely guarded. Sufficient to say that the scene is split up into a matrix of metering zones (between 30 and 200), each of which are evaluated individually, the overall exposure is based on an algorithm specific to that camera. Matrix metering often offers the best exposure possible."