The direct answer
Most social platforms allow exactly one clickable link on a profile, and none in a regular post caption. A link-in-bio page works around that. It is a small, single page with its own URL, listing several links: your shop, your latest video, your newsletter, whatever matters this week. You put the one link platforms allow in your bio, and it fans out to everything else from there.
Why the workaround exists at all
Every post says "link in bio" for the same reason: there is nowhere else on most platforms to put a clickable link, and a caption full of a raw URL usually gets ignored or actively suppressed. A single, stable bio link that leads to a small page you update whenever you want is the practical fix.
What actually belongs on one
Kept short works better than a long list nobody scrolls through. Common contents:
- Whatever you are promoting this week: a new post, a product, an event
- A handful of evergreen links, such as your shop, your newsletter signup, and your other channels
- Contact information, if you take business inquiries through it