To keep track of the multiple groups that attend your event, go to Segmentation under Reports (Enable Reports under Power Ups if you have not already done so), create a new segment, choose a contact type viz. attendees, speakers, authors, reviewers etc., choose the associated fields with which you would separate the groups, and Save.

For example, to create a list of a group of attendees who are female and are from New York, you would need to select the usertype attendees, then select female filter from the Gender field, select New York filter in the State and Country field, and then save. After saving the segment, go to the list displaying all the segments, click on View Segment and you shall see a list of all attendees who are female and from NY.