Rush/Pref Parties

I will be going through rush this fall and I know there are parties or something where you get to meet the actives, but I don't know what it's like(is it a regular party w/ music and stuff or is it little get to know you activities?) Another thing I would like to know about are the pref parties. I know you get invited back for that if the sisters think you could help the sorority in some way, but I have no idea what it's like. Is it just like the parties during rush? I would love any help you could give me on this. Thanks.