There are so many databases because there is so much information. There is no one database that covers all the resources available. Some databases will be directly focused on your subject, while others, such as Academic Search Complete cover a wider range of subjects so are useful for multi-disciplinary topics and topics that don't fit a specific subject.
Which databases you use depends on what you're looking for, it's a good idea to start with Search + Find because it indexes a large number of our collections.
Type in your keywords, when you find the article or document you want, click on its title. You will need to login using your GMIT email address and network password. This will bring you into the e-resource where you can view or print the article.