What happens when I turn off the setting - ‘Admins approve new member requests’ in a public group?

Any person using Hike can search, find, and join a public group. If you switch off 'Admins approve new member requests', anyone on Hike will be able to join your public group.

But, if you want to control and limit people joining your public group, you can switch on this setting. Then, you and the other admins of your group will approve the requests from new people willing to join the group.