Wikipedia's explanation is a little outlandish, as though these are actual creatures out there. It's frustrating that useful knowledge always gets obfuscated by idiots.
Psychic vampires are just every day people who latch onto you through various means and take your energy. If you're really sensitive or have a rather pure spirit, these kinds of people will be attracted to you everywhere you go. Most of them don't even know they're doing it.
The most common ways they do it is through emotional neediness, talking incessantly, or through uninvited body contact. All methods take energy. The talkers are the worst because even after you give social queues that you need the conversation to end, they keep talking. I've learned to be very firm with such people. It also helps that it's part of my profession, so if they want to keep talking beyond the allotted time I just increase their fee
And for the empiricists, it's not that the material interaction is draining, it's that they are actually weaker than you and taking from you on a very subtle level. If you're a sensitive person that lacks boundaries, you'll know what I'm talking about.
You have to get good at giving the fuck off vibe or using your voice directly. Vampires are usually attracted to people who can't say no and are very self-sacrificing in general, so if you find yourself in those situations a lot then you need to learn to protect yourself and put your foot down. They really don't care, they'll just keep taking and taking until there's nothing left, because they aren't really dealing with their own issues.
Old people 65+ are the absolute worst.