Unidirectional movement

(movement in a certain direction)

Non-directed movement,

or movement in various directions

брести

(to roam, to wander)

нести

(to carry (in one's hands)

катить

(to roll, to wheel, to bowl)

The verbs of unidirectional movement are used:

1) If at the moment of speech the motion is observed to go on in one direction only:

Я иду в институт.

I go to the college.

2) Talking of habitual movements in one direction:

Осенью перелётные птицы летят на юг.

In autumn migratory birds fly to the south.

3) In the case of a concrete instruction, command or advice to make a move in a certain direction:

 Идите сюда!

Come here!

The verbs of non-directed or variously directed   movement are used:

1) If at the moment of speech the motion is observed to go on in different directions:

Он ходит по комнате.

He is walking about the room.

2) Speaking about somebody's habitual movements in different directions:

Каждое лето мы ездим на юг.

Every summer we go to the south.

3) Speaking about a movement in two different direction (there and back). The verb ходил is synonymous with the verb был:

Где ты был? - Ходил в институт.

Where were you? - I went to the college. (I go there and then come back)

4) Speaking of ability, skill, of some usual means of locomotion:

Он хорошо плавает. - He swims well.

Змеи ползают. - Snakes crawl.