In information systems, a tag is a non-hierarchical keyword or term assigned to a piece of information (such as an Internet bookmark, digital image, or computer file). This kind of metadata helps describe an item and allows it to be found again by browsing or searching.
To put it simply, MyStickies allows you to place little yellow squares of digital paper anywhere and everywhere you feel like in the whole wide web. Along with the ability to put sticky notes on webpages mystickies offers a powerful interface to browse, search, sort, edit and generally have a wonderfull time with your sticky notes from any computer that has internet access.
Zotero is the only research tool that automatically senses content in your web browser, allowing you to add it to your personal library with a single click. Whether you're searching for a preprint on arXiv.org, a journal article from JSTOR, a news story from the New York Times, or a book from your university library catalog, Zotero has you covered with support for thousands of sites.