Hasta La Motion!

Hi, ive been doing some research into visualy effects in film and it seems to be an area i would really like to move into. I have a basic understanding of the relevant roles but i was wondering if someone could help by defining all the different positions that are available in film vfx today (i.e rotoscope artist, compositior, matchmover etc) and also what the people in these positions would be responsible for? My interest currently lies in Particle/ fluid effects, is there a position soley for this or does it come under a more general position like 3d Artist or compositor?

Thanks