Catboy (Connor): A cat-like kid with super-speed and great hearing abilities. He is the leader of the trio and drives the Cat-Car. His suit is dark blue in color and has ears and a tail.
Owlette (Amaya): An owl-like girl with flying abilities and a special ability to see things from far away using her owl eyes. She is the only female member of the group and flies the Owl-Glider. Her suit is red and has an owl mask with feathered wings on her back.
Gekko (Greg): A lizard-like boy with super-strength, the ability to climb walls and ceilings, and the ability to color-change and camouflage. He is the youngest of the trio and drives the Gekko-mobile. His suit is green in color and has reptilian features.
PJ Robot: A robot with the ability to hover above the ground. He maintains HQ, acts as mission control for the team, and occasionally accompanies the heroes on missions.
In general, the traits for the team appears to be an inversed version of their picture book counterpart's personalities.
Here are the key differences:
The PJ Masks act more chivalric and mature than Les Pyjamasques, and disallow any childish and immature behavior that the other characters show (e.g. trash talking, mockery, mean tricks, acting sneaky, cheating etc).
They encourage others to follow their ideals on acting more nicely and less childish.
They act more like kids of pre-teen and teenager age rather than behaving like average kids.
The PJ Masks had moments of clashing with each other (including other characters on some cases), which is something that is the opposite of their book counterparts' more efficient and determined trait.
This behavior often resulted the villains getting the better of them until they realize the mistakes they made and work things out.
The PJ Masks heroic deeds appear less extreme and more merciful than Les Pyjamasques due to their chivalric behavior.
Unlike the other heroes, they don't give the villains any extreme punishment, and prefer to allow them to flee once their plan is thwarted. However, on a few occasions, they will often confiscate the villains' weapons.
In most cases, the PJ Masks' prefer to only use their powers to attack the villains rather than incorporating tactics that are related to hand-to-hand combat.
Unlike Les Pyjamasques, it is unknown when and how the PJ Masks got formed, but it is confirmed in "HQ Tour" that their adventures on saving the day started in "Blame it on the Train, Owlette", though it might've been way earlier than that.
In "PJ Dylan", it was thought that Armadylan was an actual member of the trio, but this was resolved at the end of the episode when the PJ Masks decided that he can help them once at a while (but not as an actual member).
Their catchphrases, usually said by either Connor, Greg, or Amaya, is "PJ Masks, we're on our way. Into the night, to save the day!" or "Pyjamasques, on a un nouveau défi, les soucis, on les règle la nuit!" (in the French dub).
It is possible that when they switch at nighttime, they start thinking more like animals. They are able to trot on all four legs like an animal would, have catchphrases (and insults thrown at them) that relate to the animal they're based off of, and are able to get into poses that the animal they're based off of would be able to.
The only PJ Masks shown in the current trio that does not have a tail is Owlette and PJ Robot and this can be seen if one looks at their poses thoroughly.
According to a YouTube video from the official PJ Masks channel, the PJ Masks are all 6 years old (the description reads "Six year olds Connor, Amaya, and Greg", thus confirming Les Pyjamasques' age). The villains' ages are currently unknown, but they could be around that age as well.
Whenever their powers are activated, their costumes will glow a lighter color of their signature colors. They also usually call out the names of their powers upon activating them, but not always.
Other characters who have that similarity is Yoyo (although, his costume would no longer have the glowing feature in his later appearances).
The PJ Masks would choose to act casual, discreet and blend in from the public such as hiding or disguising their voices so that no one will know who they really are.
The PJ Masks' group name and member names were eventually adopted as nicknames for Les Pyjamasques by fans outside France, despite the PJ Masks and Les Pyjamasques being considered separate characters and group by continuity.
Some of the fans ignored the fact that PJ Robot is the "fourth PJ Mask to the team", and refer a new character they suggested to be added to the TV series as a "fourth PJ Mask" member.
Armadylan, An Yu and Newton Star are not actual members of the PJ Masks, but rather allies of the team who sometimes help them.