Although Peng Yanjia already said what each skill can do, I gotta need to break up about its overall stat:
Forest Extreme Dragon stat
Flies past buildings.
Constricts a target by throwing a deadly vine net at it, dealing high damage. Best used against other giant units like other extremes, gods and colossus.
Ever needing a Venus to do the work? Spawns a swarm of flytraps to eat up smaller units (below 500HP or something), and damage nearby large units that can't be eaten. If you have Forest Elemental God, you should be familiar with its skill.
Whirlwind of Bugs
Unlike other Extremes and units that use this kind of attack, FBD is currently the only other unit that also spawns nasty little buggers called Forest Bugs in swarms of 10 that attack hostile targets. It won't stay for long though, as it will die over time, regardless of its total health. (They flip like cockroaches when they die.. cute. lol)
If spawning mobs to harass your opponent is one thing, then this dragon is for you, since its whirlwind not only hits any units close to its range, it also spawns those buggers to distract them.