Hardtail mountain bikes are bicycles with a suspension fork in the front but without any suspension in the rear. This makes them a popular choice for riders who want a bike that is lightweight, efficient, and capable of handling a variety of terrain.

Rigid mountain bikes, on the other hand, have no suspension at all. They are lightweight and simple, making them a great choice for riders who want a bike that is easy to maintain and offers a pure, unadulterated riding experience.

Overall, the choice between a hardtail and a rigid mountain bike largely depends on the rider's preferences and intended use. Hardtails are better suited for more technical off-road riding, while rigid bikes are great for commuting or casual off-road use.