Drag bubble camps are where the enemy place a warp disruption bubble (the anchorable type or maybe a heavy interdictor) say 50km behind or in front of the gate.
The mechanics of these bubbles mean that if you warp relatively in line from another point in space these bubbles will pull you out of warp into the bubble rather than at the destination you were warping to.
So say you emerge at a gat in a 0.0 system, you initiate warp to another gate say 50AU away and if there is a bubble setup 50km behind the outgoing gate inline from where you came from, you would not drop out of warp on the gate, but in the bubble. And waiting for you will probably be some nasty ships who want to kill you.
If you are in a large ship these situations are deadly (unless you have backup) if you are in a small ship you may be ok. Just MWD and burn away, overload your MWD helps.
The other kind, bubble camps are where an enemy sets up multiple overlapping bubbles on a gate. Say you jump through you will emerge in space 15km roughly from the gate and sadly if the enemy are clever with the positioning of the bubbles you will immediately find yourself unable to warp out due to being in a bubble. These are slightly easier to escape, but only slightly.
Again if in a big ship you will generally die. If you are in a small ship MWD back to the gate, however the trick here is to hold your cloak as long as possible after jumping to wait out your session timer.
If you panic, hit MWD to the gate, even if you do make it back you will possibly be prevented from jumping by the time limit between session changes (session timer i.e jumping between systems etc.) so hold your cloak to wait out the timer, MWD under overload and spam the jump button.
If you have good spatial awareness and a fast warping ship however you can possibly look for gaps in the bubble and take a chance at warping out while in one.