The frame is sturdy, with a geometry similar to a mountain bike, but with a more upright seating position than a mountain bike - less strain on the arms and better visibility. Designed for longer journeys, often adapted for mounting various accessories: mudguards, racks.
Material - aluminium, the most common. Lighter than steel and stronger than carbon fibre. Used in various types of bicycles. It has the best value for money.
The wheels are robust, suitable for a wide range of terrains and for fitting wide tyres. Ideal if you like to ride on tarmac as well as on forest paths. The 28" wheel size is suitable for longer journeys.
The chain is partially hidden under the chain guard, or a scratch guard is placed on the frame. Usually left fairly open for easy access when changing.
Plastic mudguards are often added to keep the overall weight of the bike to a minimum to accommodate the optional luggage rack.
Saddle narrower, stiffer (compared to city bikes) for a sportier seating position.
Both dynamos for comfort and separate battery lights to maintain a lighter construction.