From what I learned in the first half of the first book, there are 4 girls that are best friends. Around age 12 or 13 I guess. They are going to be split up for the summer (vacations, family stuff, etc.) for the first time and want a way to stay in touch.
The 4 girls are very different in personalities, interests, and body shape. But they find these blue jeans that fit all 4 of them perfectly. So they wear them part of the summer and then send them on to the next girl to wear. They have this whole ceremony to declare the sisterhood.
My boyfriend thinks this is the weirdest concept ever. I tried to explain how this is totally what 12 year old girs would do in real life, but he just says there's no way he would share pants with his friends.
