"Citation Searching" is a term used for starting from a particular information source and finding other information sources that use, or cite, the original source in their bibliographies/references.
Citation Searching is the logical opposite of looking in the bibliography of the source you have in order to find related articles: you find related articles by looking for it in other bibliographies.
Using the bibliography of a paper, you can look backward in time; using citation searching to go forward in time.
There are several database/search engines that allow citation searching. Among them are: