I am planning to buy a GPS I know nothing of what it involves to get it going. where does the power supply come from and etc?

Like in order to connect to the company’s satellite, to receive updates, etc. Or do you just pay for the GPS unit and everything else is included?

I have heard of GPS devices that can be put into a car and mounted on the windshield to access satellites and can also be used by a person walking in unfamiliar areas such as foreign or domestic cities. Does anyone know the names of such a device and also an approximate price?

Where do you store your gps after you’re done using it?
Are there other alternatives to viewing your gps in your car rather than the mount?
Is it ok to store your gps in your car during a hot day?

I trail ride in heavily wooded areas. I would like to start doing some riding off the beaten path. I am interested to know what handheld GPS units some of you use. Which GPS gets the best reception under heavy tree cover? What about value for the money?