Full-text databases include full-text of the material, as well as references
Reference databases include references to articles, but not necessarily the articles themselves, which often must be retrieved elsewhere
Citation databases include information on citations between articles: who has cited what and how many citations have accumulated
Please note that most databases are combinations of these types. Some of the articles in the database can be read in full-text, some are available only as abstracts.
You can easily access the library's e-resources by using Google Scholar's library links. When you have activated the library links (Google Scholar -> Settings), your search results will include fulltext links for articles your university subscribes to. The library links are also accessible via remote use, so you don't have to check the availability of the article in Nelli separately.