This information is meant to be the biggest selling point of your selling activity - the "why" behind your mission and goal. It will appear once someone has landed on your Activity Homepage. Write your strongest description of what you do, why you do it, and how the students will benefit from being a part of it.
Often, you already have this information somewhere (i.e. flyer, website, etc.), so there is no reason to reinvent the wheel in this description. Feel free to copy and paste your existing message that you have used to promote your program in the past.