The "Requesters" field, also called the "e-mail" field, contains the e-mail addresses of the people for whom the work is being done.
That is sometimes different than the person creating the request. So if you're submitting for someone else, please change the field to contain the address of the person for whom the work is being done. Your name will be automatically recorded as the author of the first transaction.
The field usually starts with one name, but multiple requests for the same work usually result in the requests being merged into a single request.
If a simple userid is provided, then it will be treated as an @uwaterloo.ca address if it's registered as such, otherwise it will be used as is, which means that it had better work on the WWW server on which ST is running. So, mail sent by ST for an item assigned to "accounts" (for example) will be to "accounts@cs" if the cs.uwaterloo.ca version sends it, and to "accounts@math" if the www.math.uwaterloo.ca version sends it.
When specifying this field in a customized sort or display, any of the names "requestors", "Requestor" or "Req." can be used.