smoothly and there is no additional resistance, but they go all the way to the bar without moving the pads much when pulled, then it is likely a bad bleed. If the lever moves as normal, stops well short of the bar and gets firm but the pads aren't moving, then it's likely dirty/sticky pistons in the caliper. The pistons are located directly under the brake pads. Over time dirt and crud can get in there and foul the seals and such and make the pistons sticky. This usually manifests itself in a pad that won't retract completely and stay incontact with the rotor when the brake lever is released. If you know little about hydraulic disc brakes or have never worked on them before I would highly suggest taking the bike in to a good shop and have them look at the brake(s). While bicycle disc brakes aren't rocket science, they are a bit technical even though they are quite simple. If you don't know what you are doing you could end up with a bigger mess than you started with.
Either way it is a realatively easy fix IF you know what you are doing. If not then some help from a friend that does, or taking it to a shop is highly recommended.