I don't know whether the Beears will be running it, but since you asked...
Here's the 4-3 Under front that our front-seven has been using for the past ten years or so:
It's the same front that most 4-3 teams run as their base. The linemen all line up in a gap, and everyone in the front seven is responsible for one gap. The job of the linemen is to penetrate the gap first and then diagnose the play.
Here's a two-gap (or Bullough-Fairbanks) 3-4:
The three linemen are lined up directly in front of an offensive lineman, and they're each responsible for the gaps on either side of those lineman. The three linemen are able to cover 6 gaps, leaving the linebackers the freedom to roam and make plays.
Now, here's a hybrid front:
The right end and 3-tech tackle are lined up exactly like they are in the 4-3 Under above. The difference is that the left side of the line is playing like a two-gap 3-4. The nose tackle is shifted in front of the center and the left end is shifted in front of the right tackle.
Because the weak side "a" gap is now being controlled by the nose tackle, the Will linebacker is able to chase down plays without worrying about a gap. The same thing goes for the middle linebacker. He's no longer responsible for the strong side "b" gap.
This is the same hybrid front that the Seahawks, Ravens and Patriots use. It's essentially a 4-3 front with two lineman two-gapping.