When it comes to understanding the types of mountain bikes that exist you you can divide them into so many different types of categories that it can get very confusing as to exactly what type of bike to buy. As you become more experienced, you may find yourself gravitating to a certain type of mountain bike. Or you may even find yourself wanting more than one bike in your garage to cater for specific riding disciplines.
But when you're just starting out in the sport you'll more than likely just stick to having one mountain bike in the garage - at least for a little while. So what type of bike should that be? Let's start at having the first categories you're going to come across: Hardtail vs Dual Suspension.
In case it isn't obvious (but I'm sure it is), a hardtail has no rear suspension while a dual suspension has the ability to absorb bumps at the front and back. Hardtails have a few advantages, particularly on the cost side of things. They can be much cheaper to buy and also have a lot less moving parts making them cheaper to maintain and have less things that can go wrong. They can also be a lot more efficient to pedal, with the power of each pedal stroke going straight to driving you forward and not being absorbed by the rear suspension of a bike.
The main disadvantages of a hardtail? Well, they're generally less comfortable to ride than a plush dual suspension, which can also make them more fatiguing over a distance to ride. And without any rear suspension to absorb bumps, riding a hardtail over technical terrain will likely be a lot more challenging - so understanding the types of trails that you'll be riding is important. That being said, with the right level of skill and fitness you can take a hardtail almost anywhere while having a lot of fun doing so.
Despite the cost and complexity that comes with a dual suspension mountain bike there are definitive reasons to invest. One of the main reason is that having suspension front and rear will make riding more comfortable and often less fatiguing, particularly over rough, technical terrain. It can make the whole mountain bike riding experience a lot more comfortable and enjoyable for you. That's actually pretty important given that you can spend hours sitting on what is generally a pretty uncomfortable seat!
The other important point about dual suspension bikes is that for most riders, they are generally much more capable and forgiving over a variety of terrain than a hardtail. Granted a skilled rider can probably ride a hardtail over anything, but for a lot of us, riding a dual suspension bike will allow us to ride more trails with confidence.
Moving on from whether or not a mountain bike has rear suspension are the riding categories of mountain bikes. These categories are actually based off the race disciplines that exist in the mountain biking world and are generally defined by the amount of rear suspension travel on a mountain bike (it can be a lot more complex that that but let's try and keep it simple for this exercise). Generally speaking, the less suspension travel a mountain bike has, the better it is at climbing while the more it has, the better it is at descending. Below is a very loose summary of the categories:
100 - 115mm - Cross Country mountain bikes. Efficient and light weight these bikes are great for climbing and very agile but can be a bit nervous on the descents. Ideal for XC races and for terrain where a lot of climbing is involved.
115 - 130mm - Trail mountain bikes. All purpose mountain bikes that strike a balance between climbing and descending. The 115 - 120 mm range is often popular for long distance marathon races, providing that extra comfort against fatigue than the shorter travel Cross Country bikes.
130 - 150mm - All Mountain (sometimes called Aggressive Trail) bikes. With a bit more travel these bikes still attempt to offer decent climbing ability but are aimed towards providing a rider with more confidence for the descents.
150 - 170mm - Enduro mountain bikes. Mountain bikes designed for racing downhill, but built with being able to pedal up hill to the start of a descent. Longer, slacker and stronger these are basically mini-downhill bikes that you can pedal
More than 170mm - Downhill mountain bikes. Purpose built machines designed with the strength and stability to scream down the side of a mountain. Definitely not designed to pedal up hill.
When it comes to selecting the type of bike you want, knowing the type of riding you want to do the most of is key.
To motor or not to motor - that is the question. The e-bike category has surged forward in the recent years and for many people, having a bit of assistance to get around is an ideal way to get around on the trails. The modern e-bike offers riders the ability to get around to places they might be able to normally ride without needing to be a supremely fit athlete. And these days, you'll often be able to find an e-bike at a price not to dissimilar to a mid-range dual suspension bike, making it even more appealing.
If there is one main down side to an e-bike, it's the weight with most fitting into the over 20kg range while most mountain bikes are about 14kg. The extra weight can make handling some trail features a bit trickier, although with the right riding technique you can overcome some of this issue. And of course, electronics are another point of failure on a mountain bike - there's nothing like having to pedal a 20kg bike back home when the motor isn't working... (it happens!)
Which category bike should you actually choose? Well, if money is no object, get one in every category! But the reality of most people is that they don't have that luxury. So have a good think about the sort of mountain bike riding you're going to do the most of and choose the type of bike that will give you the most enjoyment in that discipline of riding.