What is the difference between the Regular and Extended licence?

It comes down to one question: do the people who end up using what you built pay to use it?

Regular

Covers a project where end users are not charged. Your own website, a client's brochure site, an internal dashboard, a marketing page, a portfolio. You may well be charging your client to build it, and that is fine. What matters is that the finished thing is free for the people who use it.

Extended

Covers a project where end users are charged. A paid product, a subscription app, a site that sells access to the feature the item provides, anything where the item is part of what somebody is paying for.

A quick test

Ask whether money reaches you because of the thing the item does. If someone pays to get through the door of the site you built with it, you want Extended. If the site is free to use and you were paid once to build it, Regular is right.

Both give you the same files

The tier is a permission, not a different download. You get the same code either way, along with the same updates and the same support window. What changes is what you are allowed to build with it.

Sellers set the exact terms

The two tiers above are the shape of it, but each item spells out precisely what its Regular and Extended licences grant, on its own page, before you buy. Read that if your project sits anywhere near the line. If it is still unclear, ask in the comments on the item, and the answer will help the next person too.