Article-level metrics most often measure the impact or influence of a particular journal article. Other content types such as book chapters, conference proceedings, and certain other items can also be measured using these same tools.
Citation counts--You can find out how many times an article has been cited using the library databases Web of Science or Scopus. Google Scholar also contains this information. The citation count varies between different databases and is dependent upon the journals and other sources indexed by that database.
Altmetrics--Goes beyond citation count to include how often an article is discussed on social media, viewed on a website, or saved in a citation manager. Each of the services does this in a different way. You may wish to try all of them!