Purpose of EF1 alpha promoter
EF1-alpha is considered a ubiquitous/constitutive promoter; it is effective in all animal cells and tends to provide strong expression. Embryonic (and other) stem cells are more difficult to target than other cells because they don't express genes under the cell-type specific promoters that are often used for other populations of cells, which is why you're seeing it used specifically for that application, but that's not the only use.
You'll find a lot of the promoter information on individual commercial sites and rather than promoting specific ones I'd suggest searches like https://www.google.com/search?q=ef1+alpha+constituitive or https://www.google.com/search?q=ef1+alpha+ubiquitous - use of EF1-alpha isn't &quot;owned&quot; by anyone so when they say these things it's not just because they're trying to sell you on some special method of theirs, they are just using a field standard approach.