I believe it's the first of those two.
However, regardless of what the acronym stands for, the PSE versions of the VCP exams are taken only by candidates who did their VMware training with a VMware IT Academy (VITA) - an academic institution such as a college or university. Those exams are booked using a special voucher which the VITA issues to a student when they have completed their training.
So, unless you've done your training with a VITA - don't worry about PSE exams, as they're not for you.
If you do your training with VMware, or with a commercial VMware Authorised Training Center (VATC) - you'll take the regular version of the exam, not the PSE version.
The items covered in a PSE exam are the same as the regular version of the exam - it's just the administration around the exams and the certification that's different.
Thank you so much for your answer @scott28tt
very clear for me, the exam I should take it's the one with PSE.
Just one doubt, before taking this 2V0-621PSE should I take vSphere foundations anyway? Or candidates taking PSE version doesn't need to take this previous exam?
That means you must have taken your training with a VITA.
I recommend you review the requirements on this page: VMware Certified Professional 6 – Data Center Virtualization (VCP6-DCV)
You'll see that you WILL need to pass vSphere Foundations.
That's clear simply wanna to double confirm it, since PSE version of the exam are not mentioned in VMware certification page.
Thank you so much!