Always a good read
https://sheldonbrown.com/nexus8.shtml
Nexus is a family of parts, of which the Nexus Inter 8 eight speed hub is one. The Alfine 8-speed hub is a very similar, higher-end model which has a disc-brake fitting.
More info from random web search
Shimano Alfine 8
Shimano’s Alfine 8 hub was developed for mountain bike use and is designed to be ultra reliable even in extreme conditions, and Shimano say it’s their most efficient yet. Gearing is identical to the Nexus 8, though it’s only found on disc braked bikes, and shares most of its internals with the recent Nexus 8, with labyrinth seals for weatherproofing, and similar needle bearings for increased durability and high drive efficiency. The Alfine’s top-normal internal structure gives improved tolerance when shifting while riding under load, making it ideal for E-bikes and offroading, while the double roller clutch engagement also gives a smoother quieter shift.
Shimano Nexus 7
Shimano’s super-reliable Nexus 7 hub offers all the low-maintenance reliability of the traditional 3-speed Sturmey Archer hub that your grandad used, but with a much wider range and smaller steps between the 7 gears, giving gearing equivalent to an 11-27 7-speed cassette. With a typical chainring and sprocket combination of 40/19 the bottom gear is 36 inches and the top is 88 inches, enough for modestly hilly terrain. The shift is smoother and faster than the old hub gears, and you can change gear at a standstill (no more lifting up the back wheel at the traffic lights!) With no shifting between sprockets, the chain lasts ages, and can be enclosed, and the hub itself needs servicing only every two years or 5000km.