Acoustic guitar:
you need a mic, a preamp, an audio interface and some recording software.
Or
A mic, a preamp and a hardware recorder (tape or digital)
You can buy things which combine all or any of those things. Habitat has a mic that also has the preamp and audio interface in it. Audio interfaces in general have preamps built in.
Like anything, you get what you pay for.
My preferred setup for acoustic is either a Ramshackle U87 mic or a Shure SM81, a Ramshackle Tube preamp, Allen & Heath ICE16 interface and Cubase software.
Reaper is almost an equally good software IMO, for a fraction of the price and with a fully-featured, unlimited demo...
You can pick up pretty good (for their time) multitrack recorders for peanuts on ebay aswell, if you don't want to go the software route.
I have an old tascam 788 that cost about £50 off ebay. It will do pretty much everything...even has mic preamps (although I never use them).
The Allen & heath ICE16 can also record direct to a USB stick, although it has no editing features and being a fairly new product is quite pricey.
It all depends on how much money you can put into it to get setup.