Unidirectional vs multidirectional verbs.
Unidirectional verbs (eg. идти) describe movement in one direction, and mostly just a one time movement or a single occasion.
Multidirectional verbs (eg. ходить) describe repeated movements, general movement, movement in different directions and a return journey that happened in the past.
Here are a few examples with English translations:
2. Куда ты идёшь?
2. Where are you going? (Movement in one direction, one time movement)
3. Мы часто ходим в университет.
3. We often go to university.