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:

1. Каждый день, Борис ходит в бассейн. 
1. Every day (repeated movement), Boris goes to the swimming pool. 

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.