Backlink is a link coming from another website back to your own, also called inward or inbound links.
If page A links out to page B, then page B is said to have a backlink from a web page A.
Backlinks are used in SEO to increase the understanding of a website and to get it higher in the SERP (Search Engine Ranking Page).
Check Back Links online:
ahrefs.com/backlink-checker
seoreviewtools.com/valuable-backlinks-checker
smallseotools.com/backlink-checker
neilpatel.com/
sitechecker.pro/backlinks-checker
monitorbacklinks.com/seo-tools/backlink-checker
linkminer.com
rankwatch.com/backlinks
majestic.com/backlink-checker