It is common in the US for students to give their recommendation writers some notes about themselves as an aide memoire. It reminds the writer of how they know the student (what classes you have taken with them, for example), any individual moments which might stand out (a paper, a class performance, ‘only student who…’ etc ), some factual stuff (eg,the ‘top 2%’ stuff), and what you are focusing your application on. It can include examples of leadership, or overcoming a particular challenge, or a having a particular facility for X academic ability, etc. IF the writer already has direct knowledge/experience of that with you. It should be short (less than a page of bullet points), and carefully edited to help them remember what stands out about you.