Tell me which answer really give someone an explanation what it really is? You need a long ass reply. Come on. What if you spot meter someones shiny forehead? It is not an easy thing to explain and has been discussed to death.
OK sparky.. keep up the good work. Keep replying to all of those basic questions such as: what is aperture priority, speed priority, spot metering to all the people who is too lazy google it or read the manual.