From Lexicanum

The Ravenwing is the Second Company of the Space Marines Unforgiven chapters. They are designed as a fast, reactionary force primarily for outflanking and surrounding enemy formations. To enable them to work most effectivly, the entire company is mounted on Bikes and Land Speeders.

Interestingly, Ravenwing armour colours are as the old Legion used to wear, all black armour. The symbol for the Ravenwing is the claw of a raven on a shield of skulls, which is generally orange or red in colour.

The Ravenwing are the rapid strike force of the chapter and so often act as independent forces in a battle, if not striking from the rear to eliminate enemy reinforcements or artillery before they can affect a battle elsewhere.

In comparison to the Deathwing the Ravenwing is not made up of the veterans. They know some of the secrets regarding the Fallen as they are often tasked with hunting these Chaos marines down.

Only the Grand Master and Master of the Ravenwing know the truth behind the Fallen since they also are part of the Inner Circle, and while being a part of the Deathwing they don't not generally share the same stubbornness and resolve shown in the other Deathwing ranks.