These are just my thoughts on these term. These should be taken with a grain of salt (thats my serving suggestion at least).
Brand Ambassador-entry level field marketing staff. The work horses of the industry. This term applies to samplers, field staff, event staff and sometimes even labor staff. Often hired by staffing agencies like EventPro or Attack.
Labor staff- Grunts. They build stages, rig sound, prep premiums even clean event sites. Normally not interacting with the public.
Super Model-A magizine level Model. Makes a living off being beautiful. This is what most models want to be. These women live on the cover of fashion magazines. They don't get food.
Models – Hot girls hired as market staff. Often times (not allways) these are girls that have been able to slide by on their looks in a lot of ways. Usually not the best staffers. When I get a hot girl staffer that doesn't want to work and bitchs all day I think of her as a model. I prefer working with field marketer or Brand Ambassador rather then models. These women are AWESOME for car/boat shows.
Field Marketer – Someone who works hard in various experiential marketing campaigns. They are furthering their career in marketing, not just working gigs to pay bills. Often they start as Brand Ambassador then move to field manager then tour staff then tour manager then account manager then tour/event deisgner then they may even start their own company (thats just one path, there are MANY others).
Promotional Models – Models who will work harder and actually understand a few concepts of marketing. These are the hot girls that work hard and make a great day in the field. They arn't pursuing a career in marketing but the gigs they work pay the bills.
Brand Advocates – Never heard this one before. I would guess a Brand Ambassador who doesn't have any premiums to give away. Someone who is only out to re-enforce brand image
Street teams-Long term, local, guerilla marketing teams. Red Bull's local energy crews are a great example. Many radio stations have local street teams.
Lead models – Hot girls who understand marketing and can manage staffers under her.
Samplers – Brand Ambassador with samples to hand out.
Demonstrators – Brand Ambassador promoting a product that needs to be explained and demoed. The teams that launched the Nintendo Wii would be a great example. Another would be a chef that travels with a health food tour showing consumers how to cook with the clients products. Often found in retail locations.