A high school transcript is a record of your academic accomplishments in high school. It lists every class you took, when you took them, and the grade you received in each class, sometimes along with additional information such as standardized test scores and any honors you received. 

There are two versions of your high school transcript: official and unofficial. The two versions will usually look very similar or identical in terms of content, but an official transcript will often have a seal or tamper-proof marks on it or will be inside a sealed envelope. Official transcripts are required to be sent to each college for which you are applying.