PostEaseThe short answer
A UTM parameter is a short piece of text appended to a URL, invisible to a visitor but readable by an analytics tool, that records where a click came from: which platform, which post, which campaign. Without one, a click from a bio link shows up as generic "direct" or "referral" traffic, with no way to trace it back to the post that generated it.
Why this matters specifically for social media traffic
Most platforms only allow one clickable link, and that same link gets reused across many posts over time, so a plain, un-tagged link gives no way to tell which post drove a given visit. Adding a distinct UTM parameter each time a link is shared, or per campaign at minimum, is what lets you see later which content drove traffic, rather than only that traffic arrived from "social" in general.
A practical way to keep this manageable
Manually building a unique tagged link for every post is overhead most accounts won't sustain. A consistent naming convention (platform, plus a short campaign or post identifier), applied only to the links that matter most, captures most of the value without the full manual burden. Those are usually a launch, a lead magnet, or one specific campaign.