In the US, a HS transcript, at a bare minimum, will tell the names of the classes you took, when you took them, and what grade you made. It usually includes the GPA for each quarter, the year, and a cumulative (from beginning to present) GPA. Due to concerns about fraudulent documents, it usually has some security features. There are normally instructions explaining how grades are calculated (extra points for accelerated classes, etc;) and a description of what the transcript looks like. It includes the school name, mailing address, and phone number.
It's been a while since I was in school, so I'm not sure about if it lists things like sports, band, and other extracurricular activities, honor society, etc.
An "official" transcript is one mailed to the student in an un-opened envelope, which you present to someone else without opening it; or one sent directly from one school to the next, without first going to you. Some places charge for transcripts, while some do not. Sometimes students can obtain an unofficial one on the school's website.
Best of luck!