Is Kundalini a real thing or just a fashion?

Recently I have seen many people talking about kundalini and how good this is or how dangerous can become.

It sounds weird to me, because nowadays everyone talks about it but three years ago I never heard this word.

Sometimes I have the feeling that westerners take this kind of eastern concepts to exhibit them as a kind of fashion or trend. Maybe Im overreacting.

Anyway, what is all this kundalini about, because I dont really understand it neither. Is a kind of special energy, meditation, yoga??

Thank you.