The website is the official online home of a variety of maps covering France, it is a bit like Google Maps but with a few more bells and whistles.
One of the things it features is a layer that lets you see the IGN maps, which are like the UK's Ordnance Survey, providing information on walking routes and geographical features.
To find the layer within Géoportail from the front page of the site, enter a local town or village, or try with a postcode and you will be asked to narrow down your search if necessary.
Then a few seconds later the page will begin to form, and at first you will see an aerial view of your chosen spot, this looks very similar to Google Maps.
But if you look toward the left hand side of the screen you will see a small orange folder, named Cartes, click on this and you will see Cartes IGN, click that and you will see a map overlay.
A little further down that left hand column there is a tool that allows you to blend together one or more layers, so you can overlay the aerial view across the IGN map and get a good idea of where you are.
To print off a map entry, head to the right hand side of the webpage and you will see a small printer icon, click this and you will then be provided with a .pdf file that you should be able to open.
Beyond the IGN maps there are many more layers to discover, for example the plan cadastral option lets you see the borders of plots of land which could prove useful if you are buying a home.
Whatever you discover, be prepared to lose some time exploring.