what's that bike, dude? Kona sutra!
Bike touring nowadays comes in a number of different flavors.
There's the traditional bike touring, where you ride a road bike, the frame of which has altered to geometry to make it more cmforabtle (read upright), to ride over long distances. These bikes can be loaded up with front and back racks and panniers, and are geared to let you spin all day carrying a heavy load. These bikes are stuck to following wherever the tarmac goes, and not much more than that. They may be sturdy, but you also don't want to take too many risks with something breaking.
Or, you could bike tour in a more minimalistic style, foregoing the panniers for a large saddlebag, which will hold a limited amount of stuff (t shirt, shorts and underpants). No camping with this style.
There's also 'bikepacking', which is a play on 'back-packing'. Normally on a bike which can bounce around happily on rough roads and mountain bike trails, and carry a good amount of weight, and still be comfortable to ride. These bikes, you can often load with a large saddlebag, a bag which sits in the middle of the frame (a frame bag) and also a handlebar bag to carry the littler things you might need.
These bikes are often mountain bikes, but you can also find some which a based on a CX or gravel-riding frame and geometry.
The bike which I've used for all the touring I've done so far is the Kona Sutra. Kona have been around for 30 years, nd originated in the NW USA and Canada. They're particularly well know for tough MTB and CX bikes (and dabbled unsuccessfully in road bikes). The Sutra is their simple tourer, which brings DNA from the MTB and CX world to a touring machine.
It has a relatively high sitting position (more comfort), a high clearance bottom bracket to help bounce through rough terrain (from CX), a heavy steel frame (to provide strength), a triple ring at the front to cover a wide range of gradients and loads (from the road bikes) and a wide ranged cassette to also help with this), and friction based gear levers for simplicity if something breaks. It's disc brakes are stolen off their MTB set up, and are mechanical, again, easy to fix if something goes wrong. The wheels have a tonne of spokes (for strength), come with 42 mm tubeless Schwalbe Marathon tyres (to help prevent punctures) and are 700c/29" to help you roll over and through everything. I was running around 40-45 psi on these, which felt great.
It's a solid, heavy, bike with comfortable geometry which can take you absolutely anywhere.
And I've taken it anywhere.
For this trip, I used a saddlebag plus a couple of backpacking waterproof bags to hold my sandals and pump etc. If I were to do this again, I'd try and figure out another way of carrying these, since they tended to act as a parachute on the descents - because they are right at the front.
Otherwise this bike did, and does it all.
The tyres are smooth enough to roll well on the road, and they have enough grip to pull through gravel, rocks, as well as the nasty mud which I found leaving Siena and heading to Firenze. The frame allows me to slip into a TT position when cruising on the roads, or sit up to look at the landscape, or ride standing for MTB trails ascent or descents.
I've always loved, and bought Kona, and this bike is just a do-everything. Incredible. And only $1700 to boot.