"Power" switch

I have a "like new " 1990 Toyota Camry LE, in showroom condition, with only 90,000 miles on it. This is the first winter out of 17 that it has seen snow. In trying to learn all about the car and what we in the Northeast(Maine) expect from our vehicles and what we need to learn to get max use of the car's features I would like to know anything and everything about the "Power" button. I do not think that the instruction book gives enough information. Can someone help me. I want to know when to use it, how to use it, when not to use it, and how not to use it so that I do not abuse it and break something. This is the best car, even had new cars, not toyota though, and this little car is super in the snow, always starts, etc.etc. I just like it, a little silly I suppose but I only paid $2500 for it. Thanks.