There are two college application aspects. First of all, it must contain hard data and facts such as transcripts and test scores. The second part is appealing to the letter of recommendation for high school students, extracurricular activities, volunteerism, and personal essays.
There is one target of these letters: to provide college admissions counselors with a clear vision of who you are as a person and a student. So they give colleges insight into your character and personality.
High school recommendation letters typically discuss how long the teacher knows the student and the kind of relationships they have between each other, data about the study and work habits, and the academic targets you have. Thus, you will wish to select a coach, boss, or teacher that you have known for at least 2 years.