Data Streams act as conduits which will take Vault Hunters from one area of the map to the other. They are found in The Nexus and Motherlessboard. Typically Data Streams will come in pairs, with a blue stream going to/from an area, and an orange stream going the opposite direction. There are two orange streams in Motherlessboard without companion blue streams, though, and there are some short vertical streams (used as elevators) which don't have companions as well.
Enemy mobs appear to be unaffected by Data Streams, but if a Vault Hunter steps or jumps into one, their motion will be arrested and they will proceed to be pulled along the Data Stream's path at a sedate pace. The Vault Hunter retains some midair direction control while in the Data Stream, and can use a gravity slam to leave early if desired. Note, however, that using a gravity slam from above a Data Stream will not allow the Stream to catch the Vault Hunter, and the Vault Hunter will instead just pass right through it.