A: Hello Misty - The button is used to release the spring so you can adjust the resistance setting. If you push the button you can pop the spring out and select different levels. Thanks for reaching out to us. - Stacy
A: When you collapse the spring into the handle for transporting the button releases the spring
A: Says 15 - 25 lbs (6.8 - 11.3 kg) so I'm assuming the middle is 20 lbs