Ok, it is an activity of my english book, so, you probably don't understand about why. 

This is one of my favourite photo. I like this because I was having a good day with my boyfriend (he wasn't a boyfriend at that time), and I was happy and smiling truly, even though I wasn't so pretty and I was very chubby, it is a good memory of a good and beautiful sunny day in the park. I really like this memory and how he managed to capture my state of mind in this photo.