See requires no attention or focus from the person doing the seeing. It takes a direct object without a preposition. Look requires conscious effort on the part of the person doing the looking. An object of look, if expressed, must be preceded by a preposition (usually at, over, or for).
We saw the prototype of the new robot
standing in a corner of the office.
After watching the promotional video, we looked
at the prototype of the new robot.
We studied the specifications carefully, then looked
over the prototype of the new robot.
We looked for the prototype of the new robot
in the promotional video but could not find it.
See also hear/listen.