Here is a resource page that can help you understand TNR - Trap/Neuter/Return and community cats.

 

Why Trap-Neuter-Return Feral Cats? The Case for TNR

Spay/Neuter: Good for Cats, Good for Communities

 

How To Live With Cats In Your Neighborhood

 

The Vacuum Effect: Why Catch and Kill Doesn’t Work

 

Feral Cat Health Analysis: Living Healthy Lives Outdoors