Cloud mining consists of renting a specific hashing power provided by an entity (e.g. cryptouniverse) that owns one or more mining farms around the globe.

But what do cloud mining companies gain from it?

It may seem strange that if the earnings are so high, companies sell a similar service rather than take advantage of it, but by selling the hashing power, the money they have invested returns faster and more when you go to withdraw, the companies hold a part (tax) which covers the costs of electricity, maintenance, etc.