Who has written key articles in your field? Citation indexes track the references in published papers so that you can see (by the number of citations to a paper) who has written key articles.
Have you found a brilliant article and are wondering if other researchers are working on the same topic? Citation searching also shows you who has used a individual article in his/her own work and is therefore building on the earlier work.
Who has cited a reference? Who is citing your articles? How many times have you been cited?
For detailed guidance on which databases to use see our guide on How to Find Citations.