In my experience, a good cohesive jam is part of preparation for being a band, like a "school" for people who want to be in a band, but I agree they are not the same in a huge number of ways.
That said, we consider our band, which has been active performing and recording since around 2008, to be a "jam band" in that we each approach our songs and performances similarly to how we would in a jam. We do practice, unlike a jam, but like a jam, there are not set arrangements that have to be followed by anyone. We plan general things, but not the minute details, and we heavily use body language and signals to identify what or who goes next. We do practice an informal "form" for each song, but each artist ultimately determines what they will do at the time of the gig or session. After having played together for 15 years, the result is a quality, somewhat random, extremely high energy performance that is actually fun to do.
Because of this experience, our definitions of "jam" and "band" are probably not exactly the same as everyone else. But our definitions do work for us.
That said, we consider our band, which has been active performing and recording since around 2008, to be a "jam band" in that we each approach our songs and performances similarly to how we would in a jam. We do practice, unlike a jam, but like a jam, there are not set arrangements that have to be followed by anyone. We plan general things, but not the minute details, and we heavily use body language and signals to identify what or who goes next. We do practice an informal "form" for each song, but each artist ultimately determines what they will do at the time of the gig or session. After having played together for 15 years, the result is a quality, somewhat random, extremely high energy performance that is actually fun to do.
Because of this experience, our definitions of "jam" and "band" are probably not exactly the same as everyone else. But our definitions do work for us.