I thought it said free timed admission? Why do you buy tickets? Can't you just walk around the outside area? And how will that work with tickets if you have a whole group?

You can just walk around.

We walked around...which is free. There was a very long line to get into memorial so we got online and chose a later time and bought our tickets. It was a good idea! We didn't have to wait in line and got in early. Just showed our tickets on my phone and got right in.

Yes, need to pay for the guided tour and to see the museum. As the lines tend to be long and are often outside, be prepared if it's rainy and/or cold.

Free to enjoy the memorial, walk the garden, and enter the shopping area. Only have to pay for guided tours and if you want to go inside the museum. Plan that trip though as the line was very long when we went.

Walking around the memorial is free, tickets are for going to the world trade center observatory and the museum.