High schools send profiles to colleges to help put students in context. That way schools can see that student A took only 1 AP course while the school offered 10. Student B took 3 AP course when their school only offered 3. One student pushed themselves to take a more rigorous schedule than the other.
It also can show that a student came out of a high school with overall much lower standardized test scores than average - making their high score stand out even more. There’s also a difference between being in the top 5 in a high school where only 30% of students go on to college versus a high school where 98% go on to college.
As said above, every college is going to have their own way of interpreting this information. But it does help an adcom better understand a student’s transcript.