Put GPS in the search function...towards the top right hand side, just under your name.
This subject has been covered many times and there is a lot of good information.
My view is that if you tour on a bike they are great. I have had GPS on the bike for about 4 years. Used my TomTom to ride from the UK, through France and over the Swiss Alps into Italy and then back to Denmark in the summer.
Do not just think of GPS though. I also use my phone with mine as well as loading music onto it.
Steve