is what it means in non football terms.
A team is located near another team and then. A visiting team can make one trip and play team A on Thursday and Team B on Saturday. Instead of 2 round trips - one circular trip with an extra stop.
In all sports it means you get one game every other year where it is a very short trip - USC UCLA for example. UW WSU for example. Oregon OSU for example. Arizona ASU For example. And u Colorado as a bit of an artificially assigned one.
Then - in more cases than not - u get a rivalry game out of it. Some of those are natural and thus more meaningful than ones like u and Colorado.