"Web Based" means family tree software and information is kept on the website you choose to use. You are not buying software to download to your computer.
Here are 4 of my favorite primarily free web based family tree programs. Each offers a free sign up and lets you create your tree for free. See which one best fits your needs. I like web based programs rather then buying a family tree software program to download to my computer. I have had a software program in the past and spent endless hours inputting names and data on it. I didn't back up it up or save the information some place else and all my names, data, and information that I had was a complete loss when my computer was infected by a virus. That can't happen if it is a web based program. Not only that but finding time to work on my family tree was and is always difficult. It is nice sharing the family tree with other family members and having help.
Ancestry Online Tree Maker
If you use a free web based family tree maker and think it should be included on this list please post a comment.