Feral cats are outdoor, free-roaming cats who have never been socialized to humans
and are living in a “wild” state.
This could be a formerly domestic cat who has been abandoned and has reverted back to a wild state
or a cat who has been born on the streets and has never had any contact or interaction with humans.
Feral cats look like regular domestic housecats,
but, because they have never been socialized, they are very fearful and distrustful of humans.
Some arch their backs and hiss and show aggression; others avoid eye contact and just run.
True ferals cannot be picked up or handled. Very often, you can’t even get close to them.
From the ASPCA's website: What is a feral colony?
A cat colony is a group of free-roaming cats that live in close proximity to each other.
Colonies are often formed around shelter and a food source.
They live in the shadows—the alleyways, empty lots and condemned buildings—of almost every
neighborhood. Their lives are short and usually harsh. They struggle to find food and water in an
environment filled with the constant threats of disease, starvation, cruelty and predation.
They are the abandoned, the lost and the wild—and they need our help.
What is TNR?
TNR stands for Trap-Neuter-Return. I suppose this could also be known as Trap-Blood Test-Vaccinate-Sterilize-Release. TNR is the humane trapping of unaltered feral cats, spaying or neutering them, and then releasing them back to the same location where they were.
TNR is promoted and endorsed by the ASPCA & the HSUS (along with many, many others). This process has been proven successful at stopping the birth of new cats in a colony, managing and reducing the number of cats in feral cat colonies.
Trap-Neuter-Return starts with the Trapping of feral cats. The cats are then taken to a vet or a TNR facility while still in the trap. Males are neutered and females are spayed. While the cat is under sedation the cat's health is checked, it is blood tested, vaccinated and "ear tipped". The "ear tipping" is so that the cat can be easily recognized as having been trapped and sterilized. Just a mere quarter inch of the ear tip is removed. The cat is placed back into the trap while it recovers from the sedation.
Once recovery is complete the cat is returned to its colony and set free.
From the ASPCA website:
How Does TNR Benefit the Community?
TNR helps the community by stabilizing the population of the feral colony and, over time, reducing it. At the same time, nuisance behaviors such as spraying, excessive noisemaking and fighting are largely eliminated, and no more kittens are born. Yet, the benefit of natural rodent control is continued.
For in-depth information please check the websites of the pros on feral cats and TNR: