Who/what are The Dragons?

The Dragons are a large group of fed-up vigilantes with the goal of saving the environment, they started out as a small group of like-minded friends and eventually grew in numbers as they recruited more people. Recruits can be anyone from anarchists to people who just want to get away from their current life, as long as they support what The Dragons are doing.

What do they do?

Go undercover, blow up buildings, threaten cities, run from the government(s) etc.
Basically destroy anything harmful to the environment and fear-monger until people will go to a certain area/country where The Dragons have agreed those people can stay, but they'll have certain people stay behind, people who will gladly care for the land and its animals.

Do they care about people too?

Yes. They'll happily destroy a corrupt government/organization to help the people, that's also one of the reasons they're trying to help the environment in such a drastic way, people can't live on a dead planet.

How do they travel?

Their mech-suits have wings attached to them that let them fly around, different size wings can do different things, I'll go into more detail about that later. If they're traveling a hundred miles (~161 km) or so they can just fly, if they need to go further they can use the larger wings (even over large bodies of water), but it's safer to disguise themself as a regular person and take a bus/boat and just carry their gear in a duffle bag.

Are they just terrorising a certain country? Or more places?

In the original storyline, every country, state, and city. However this is an open story, people are meant to make their own stories based on this and can add their own twists, so it's up to you how many places are given back to nature.

How do they protect their identities?

When in their mech-suits they keep their helmets on, when undercover they wear disguises (wigs, makeup, fake tattoos, etc.), when they're not wearing their suits but not undercover they'll wear their regular clothes but will set camp outside the city they're at/someplace else they will be unlikely to be found, or split up and stay at motels or other buildings.

Wouldn't people notice a large group of winged vigilantes flying in the sky?

When a group starts to get too big to safely travel together they'll split up, one group will continue on the same plan they had and the new group will travel far away then continue on with their goal. They decide amongst themselves who will stay and who will go. If one group is targeting a major city they may call one or more groups for backup, afterwards they'll split up again and go on their merry way.

How would they react to a traitor?

That's up to you. It's your story.