A quick look at a few bike types
These bikes do not have any suspension. It is not recommended to ride these bikes on extreme terrain. They are best suited to Green graded trails where the terrain is fairly smooth and forestry roads. These bikes are also available in electric.
Hard tail bikes to not have rear suspension but they do have front suspension. The suspension for a hard tail can range from 100mm to a crazy 170mm. These bikes are made to the category 5 standard so they will be able to handle the toughest trails. However, they will require expert line choices and perfect technique from the rider in order to make it down the trails. These bikes are also available in electric.
Full suspension bikes with travel typically in the range of 120mm to 150mm. These bikes are very efficient for climbing due to their light-weight amd can manage anything on the decent. Around 150mm is more than enough to tackle the majority of features on the trails. Extreme features will require expert line choice.
Enduro bikes have 150mm to 170mm of travel. Because of this, they are slightly heavier than trail bikes due to the larger suspension and have slightly more aggressive geometry. They are for people who enjoy climbing to the top to tackling their local trails and enjoy visits to the bike park. Their longer travel makes them a great all rounder.
Full suspension bikes with travel typically in the range of 180mm to 190mm.
These bike are a blend of downhill and enduro. They still have a high enough gear range to allow riders to climb. This is then combined with a monstrous amount of suspension travel. Some can even be fitted with a dual crown fork for a more aggressive look. These bikes are made for riders to access trails where uplifts are not available allowing them to take on any challenge and even make their own way down the mountain off piste.
Full suspension bikes with travel typically in the range 190mm+ front and rear.
These bikes are made to do one thing, descend. The aggressive downhill geometry paired with only 7 speed drive train means they're only really suitable for bike parks. The downhill bike has a unique look of a dual crown fork and a low, out of the way seat.