A branded anchor is a link whose clickable text is your company or product name, or a phrase built around it, like "Margin" or "Margin's citation export".
Most links people add naturally are branded, because that's how they refer to you. A healthy profile is usually dominated by branded and URL anchors, with a smaller share of descriptive and keyword anchors.
Branded anchors are also the safest to ask for in outreach. They read naturally in a list entry, they don't look like SEO manipulation, and they help people searching your name find you.
Example
"Margin" linking to margin.example in a list of research tools is a branded anchor.
Putting it into practice
Where to use it: Anchor text distribution checker.