A jam is an informal performance; a slam is a competition.
Poetry jams have their origins in jazz jam sessions, where musicians would gather to play together without a lot of preparation. The focus was on improvisation. Jam sessions then made thier way into both the bluegrass and rap traditions. It's from the rap/hip-hop scene (which focuses mainly on the spoken word, the music mostly serving to underline it) that "jam" made the transition to other forms of poetry.
The poetry/spoken word art presented in a poetry jam may or may not be original. The focus is on the performance and how well the poets "play" together.
Poetry slams have a very definite origin in the early 1980s. A slam consists of an announced contest where the poets show up to present original work. The MC will chose a number of audience members (usually 5) to act as judges. The MC also presents a "sacrificial" poet to perform first to "calibrate" the judges. It's called a slam because poets can be "slammed" (judged harshly). For some reason people enjoy that. Poetry slams focus on original work.
Neither are necessarily boring, although as with anything the style being presented would have to appeal to you. If you've ever seen the movie "8 Mile" the contest that Rabbit (Emenmin) kept failing at was essentially a modified poetry slam (the MC had the crowd judge rather than just a few members of it).
In fact, poetry jams bear a certain resemblence to the bardic circles I believe you are familiar with. And as I am sure you know, those can be rolicking or boring depending on who decides to join in.
What was presented at the White House was a jam, not a slam. The Press Office was very clear on that. It was not a competition.