Hesh pretty much associates with hardcore and aggressive extreme sports communities, although it can be used in looser terms by some as a synonymous term for "Awesome." :V
Hesh originates from the term "Hessian," pronounced Hesh-in, which were 18th century German soldiers hired by Britain, but was used as a negative slang term for the Metal culture kids in the 70s through the 90s. Similarly to Punk culture, they took the negative slang term around and turned into a positive for themselves. Of course, I'm being way too far in depth with this stuff.
tl;dr - Hesh = Hardcore, Aggressive, Badass. Not giving a fuck kinda comes along with it :P
Often associated with Metal, Punk, Grunge, and other harder forms of Rock