@slominer
“What does learning “Chasidus” mean and entail?”
For practical purposes let’s say starting with learning Tanya is a good start.
“What is Chasidus (does it include seforim from non-Chabad Chasidishe Rebbes/talmidei chachamim) and why would non-Chasidim learn it?”
There are non Chabad chassidus sefarim but as it is not written in Chabad fashion, you would need to learn Chabad chassidus to understand that too. Not sure if not chassidim learn the chassidus of other kreizen.
“How’s it different than non-Chasidish seforim?”
Well that’s a great range lol. Generally, because it’s pnimiyus haTorah so it gives the neshama view. For example, say parshas korach- mefarshim will be debating the technicalities of what korachs complaints were and how the story happened, chassidus will address the underlying dynamic of what does this represent in our avodas Hashem? Because everything in Torah is a lesson for us. Torah milashon horaah. For some chassidus on the parsha, try likutei sichos-the first four volumes especially are referred to as the basics. Others have more shakla vtarya. I actually go on a spiritual high when I delve into a sicha with a chevrusa. It’s awesome. I didn’t think I would say that before but now that hopefully I’ve given you cause to believe I’m a rational person, I can tell you about my sicha highs.
“As a practical matter, is it widely learnt by non-chasidim?”
Yeah.