A backlink is a link on someone else’s website that points to yours. When another site links to a page of yours, search engines read it as a small vote of confidence: one site vouching for another.
For a small business, this matters because those votes add up to how trustworthy your site looks in Google’s eyes. A link from a respected local news site or a trade association carries real weight; a pile of links from spammy, unrelated pages carries little, and can even work against you. It is quality and relevance that count, not raw quantity.
You cannot honestly buy your way to good backlinks, which is why they take work to earn. The steady practice of earning them is called link building, and the accumulated result is one of the inputs behind a site’s domain authority. Backlinks are earned off your site, through real relationships and work worth linking to, not something a rebuild alone creates.