Citation management software allows you to collect, organize, cite, and share your research citations.
Some of these are standalone programs/apps; some function as add-ons/plug-ins/ extensions for other programs (for your browser and/or your word processor). Some of these programs are commercially available (at a cost) and others are available as freeware.
Wikipedia has a page here comparing many of the different citation managers.
One example of a free citation manager is Zotero.