Hybrid is a generic term for any bike that isn't a mountain or road racing bike.
Usually means it has features of both. Larger 700 wheels,but thicker tyres. Flat handlebars and gears like a mtb.
A one stop do it all bike for the leisure or commuter cyclist. Able to go across paths and light offroad use,and even on roads. Can be tailored for a specific use by tyre choices.
Serious off roaders always end up buying a proper mtb.
Serious road users nearly always gravitate to a road bike.