Tourney: Shimano's most budget groupset, often seen on basic recreational and even kids bikes. With basic stamped steel and plastic components. Expect a plastic grip shifter and 3x7 gears at this levelAltus: Altus is Shimano’s entry-level groupset and is occasionally seen on budget mountain bikes. Again, it’s not designed for mountain biking, but light off-road use is applicable. Shimano RapidFire trigger shifters are found here
Acera: Acera appears on many entry-level bikes and offers either 8 or 9-speed gears at back, and three at the front. More aluminium is starting to be seen at this price
Alivio: Alivio is top of Shimano’s ‘recreational’ mountain bike groupsets. It offers a number of features and shared aesthetics of groupsets above it. This groupset is found on entry-level mountain bikes that are designed for medium off-road
Deore: Deore is aimed at the entry to intermediate level mountain biker and is perhaps the most popular too. Deore is durable, reliable and features much of the technology found on the more expensive SLX and XT
SLX: SLX is arguably to mountain biking as what 105 is to road cycling. It’s the workhorse groupset that shares many of the same features and performance as models above, but with a higher weight. This is often due to the greater use of steels instead of advanced alloys
Zee: Designed specifically for downhill and freeriding, Zee sits at a similar price to SLX. A little dated compared to current SLX and so has lost popularity, although its brakes are still commonly found on bikes that require greater stopping power
XT: One of mountain biking’s most popular groupsets, XT is commonly thought to offer all the performance of the top-tier XTR version, but with a price that’s far more palatable. Just about all the technology is there, including a strong use of aluminium and high-quality stainless steels
XT Di2: XT also comes in an electronic version known as 'XT Di2'. Unlike the mechanical version, which requires cables to change gears, Di2 uses motor-driven mechanics at the front and rear derailleur to provide a crisp perfect shift, every time. The Di2 version is slightly heavier than mechanical (about 90g) but is impervious to dirt and grit. Once set up, it also never requires re-adjustment
XTR: The gold standard of mountain bike. XTR uses a mixture of carbon fibre, titanium and high-grade alloys to reduce weight without sacrificing reliability. XTR RapidFire Plus shift levers have marginally smoother operation due to the use of an internal bearing. It's worth noting that the latest XTR M9100 is not cross-compatible with any other Shimano components at this time
Saint: Similar in level to Shimano XTR, Saint is considered a gravity-orientated ‘specialty’ groupset. It’s most commonly found on pro-level downhill race bikes