Goggles marked "Not Rx Compatible" don't offer any built-in prescription solution — no Rx inserts, no custom lenses. If you wear glasses, you'll need to rely on other options to see clearly on the mountain.
Your two alternatives are OTG (Over-The-Glasses) goggles, which have extra room to fit your frames underneath, or wearing contact lenses with any standard goggle. OTG goggles work for casual riders but can fog more easily and feel bulkier. Contacts give you the most goggle choices and eliminate double-fog issues between lenses.
If you have strong vision correction needs and dislike contacts, it's worth seeking out Rx-compatible goggles instead. But if you're already a contact lens wearer or your prescription is mild, non-Rx goggles open up a wider selection at lower prices — just plan your vision strategy before you buy.