Recorders Court, Witness Summons?

I was at a party and there was a lot of underage drinking. I believe the owner of the house and some others got arrested. He collected the ID's of everyone who had them. When he gave it back, he gave me a sheet saying i was "hereby commanded to be and appear at the Recorder's Court in witness of someone else's case. and that if i don't show there will be a penalty, and there will be a warrant for my arrest. I am not charged for anything, correct? And any advice when going? Do i have to testify? and once again, I'm not charged for anything, correct? As the sheet only says i have to show up to court to testify for someone else?