Hiking, in comparison to trekking, tends to be shorter trips on trails that have been purposefully cleared for hikers, or at least cleared due to the frequent passage of hikers. This makes walking and navigation easier. Hikes can be day or multi-day trips but often tend to have multiple stops at a base.
Trekking, on the other hand, tends to be out in untamed nature where anything goes. This might mean harsh weather conditions or a grueling natural environment with a high altitude or steep slopes. These trips are longer than hikes and consist of camping every night, walking all day, and not stopping until you reach your destination.