offset and backspacing

Im new to tacoma world, but I have to say that pretty much everyone here is on point and pretty insightful. Ive got a two part question here though regarding wheels in general and then ofcourse tacoma's. Could someone please expain the difference between offsets and backspacing for aftermarket wheels. Im gonna run 17x9's all around with 265/70's (saving for the lift right now to go bigger). Ive seen wheels with negative offsets and positive offsets, what's the difference and what backspacing should i look for to make the wheels stick out farther rather than tucked under the wheel well? Thanx ya'll!!!

 

a mod will move this to the wheels and tires section. search in there and you will find your answer.