Mendeley is a citation management tool that's free to download and that offers 2 GB of storage free of charge; additional storage is available for a yearly fee.
Both a desktop and a web version are available, and you can seamlessly sync data between the two versions. Desktop installation is recommended since it provides a more robust version of the tool. The desktop version is also required in order to use certain features, such as the citation plugin.
Mendeley also acts as a social platform that will let you see what other scholars in your field are currently reading. It includes features to collaborate with others, but those features are limited in the free version.
Mendeley allows you to grab web pages while you're browsing the internet and add those as references in your library as well.
Note that the UMGC Library does not provide support for Mendeley; please see Mendeley's help guides if you need help with using this tool.