I don't have one yet but I was looking at a kit from Princess Auto, which can be found here: https://www.princessauto.com/en/diy-two-seat-gas-go-kart-kit/product/PA0008926107Uhhhh that's a stock image that's not your kart, so that image doesn't help at all. Furthermore if that's the same as your kart it's a generic Chinese mini buggy, probably sold under dozens of brands.
So let's start with actual pictures of your kart.
Yea I thought that seems weird too, I haven't yet purchased the kit yet as I figured it might be beneficial to see what ideas/suggestions people more experienced than myself with go-karts would have to say about it before I take the plunge and actually buy the kit. I would guess that it comes with a keyed ignition and the CVT transmission and you just buy the engine and hook everything up and away you go (unfortunately it's never that easy though).Seems odd they say it is electric start but doesn't have an engine. Maybe it's wired for a starter. If you bought this kart you could then check that whatever engine you get would be combatable with the CVT they are providing. Probably a 30 but you know how "murphy's law" works.