ArcGIS Online is a cloud-based system for mapping and analyzing geographic information. In other words, it is a GIS in an online environment. You can't do everything online you can do with the ArcGIS software, but you can create, save and share maps online. You can also use a variety of basemaps to enhance your own data. You can use the layers available in ArcGIS Online to create maps. Just use your Dartmouth username and password to create an account, view the Getting Started video and go make a map.
If you have any problems, please contact the Evans Map Room for help.