A worm hole is the term given to a passageway that might potentially exist between two given locations in space and time. The term "worm hole" was given as a solution to Einstein's Theory of General Relativity of space and time. In conventional technology, to get from point A to point B might take millions of light years, which would be very inconvenient in terms of getting there in a reasonable amount of time. The theoretical worm hole passage acts as a "short cut" between the two vast, existing planes of space and time. A portal, on the other hand, describes an entrance of some type. A black hole and a white hole would be good descriptive terms for portal assignment. The black hole would be used as an entrance, while the white hole would be used as an exit. The existence of worm holes and portals, as described in this answer, are theoretical and unproven.