Dhyana is the 7th limb aka ‘meditative absorption’.
This is when we become completely absorbed in our meditation that it no longer becomes something we are doing, but rather something we are being. It's a lovely floaty state where your mind is tamed and you are ready for yoga's ultimate goal, Samadhi (the last limb).
Sounds unattainable right?!? Well it isn't! Think how great it feels to head into Savasana after class.... your body is brimming with awesome energy and you lie down, ready to absorb it. That's the first step! It's called a 'practice' for a reason, it doesn't happen overnight ?