A "bridge" in animal training is a stimulus that bridge a correct response to a reinforcement (usually a food reward) and is almost often a vocal communication such as the sound of a clicker or praises (Good boy!). A bridge is usually an anticipation of something positive going to happen and bridging tells an animal that they did the desired behavior and a reward is on its way.
Most of what I did today was bridging and positively reinforcing my lemurs to do the behavior I want them to do. The bridge, in this instance, is the sound of a moving conveyer belt that dispenses a treat. When the lemur hears the mechanical sound of the conveyer belt, it acts as a bridge to tell them they did the right behavior and a food reward is on its way. All the lemurs that I worked with today were very cooperative. They ran right up to the apparatus and did a lot of explorative behaviors but almost immediately knows that the chute in the apparatus drops food reward because they were sitting near the chute (this might be a biased observation on my end). Hopefully, in time, they will associate the sound of the conveyer belt as the bridge.
Have I mentioned how unbearable this North Carolina heat is?