GPS Primer

[newbie]

I am beginning to think of the boating season and was also thinking of adding a GPS/Chartplotter to the boat. Before I fire of hundreds of ??s specific to the Lake, I was hoping that someone could direct me to a website that would act as a primer for GPS and chartplotting. What to look for, what features and functions there are, what mfg are the best, etc.

Thanks in advance and love the forum