Content
Most articles in PubMed are from English-language publications. Apart from PubMed, there's also PubMedCentral. This only contains research that is financed by the American government . PubMed Europe is the European equivalent. PubMed Europe contains nearly all PubMed content, plus patents, NHS clinical guidelines and more.
Usage
How to get the full-text?
PubMed contains both Open Access articles as well as links to paid databases. By using the special link on this page, a 
button is placed near every search result. When you click on this, you directly go to the full-text of an article, when available! When this isn't the case, you get the WorldCat Linkresolver page. Here you can request the article by ILL by using the 
button. When using Google to go to PubMed, you might not get a START button