Ensolite is a brand name of Vinyl/Nitrile/Neoprene blended (also known as PVC/NBR/CR) foam. It is also sometimes called gym rubber because it is used for things such as tumbling mats.
EVA foam is a lighter weight, less expensive option than Ensolite. EVA is not a brand name, it is stands for Ethylene-Vinyl Acetate. EVA is nice and short so it often gets included in product descriptions to designate what type of foam was used. It too is a closed cell foam with insulating as well as sound deadening properties. It comes in many forms and is used for a wide variety of products including insulation, yoga mats, floor mats, camping mats, sound deadening mats, and more.
Ensolite camping pads (nice stuff!) are not going to be easy to locate. The camping pad makers are now using the lighter closed cell foams in order to reduce the weight. Backpackers don't want to carry heavy camping pads so there is no market for heavy weight products because there are good alternatives that are lighter in weight. However you can find "Ensolite" exercise mats. But trying to figure out the type of foam when buying online is difficult as it is not always part of the product description. I have an advantage in that I can tell the difference in the two materials if I go to a sporting goods store and look through the selection of mats. One way to tell is the Ensolite mats weigh significantly more than the EVA foam mats. Also the Ensolite feels spongy when compressed in a side by side comparison to the EVA foam mats. Ensolite was designed for use by NASA, the space program inspired many great and useful things that become useful products for our lives.
The foam used inside of the self inflating mattress is an open cell foam. Waterproofing is provide by the exterior covering that is made with heat sealed seams. Closed cell foams are important for backpacking for a non inflating pad. But for a bed inside of a van you can choose to use closed cell or open cell, both types have insulative R value. But you have to get very specific to find out how much R value it has. Some products test for it or at least estimate it based on tables of data, example being some of the self inflating camping pads...see REI website. Other products don't bother with it because it is not particularly relevant product information, example being companies who make foam mattress toppers.