A standard lever-controlled recliner contains a series of springs attached to a metal frame. Generally, lever-pulled recliners have three positions--slightly reclined, fully reclined and mid-range. When you pull the lever on the recliner up to the first position, the lever pulls a cord connected to the sliding frame and causes it to open--the back tilts backward a little and the footrest may elevate. The chair is locked in the position. When you move the lever to the next position, more tension is added to springs.
The springs are attached to the frame and positioned to help the recliner return to its starting position. As the recliner spreads out, the springs are stretched and naturally want to return to their starting states. When you sit up, the chair will begin to close slightly, and when you sit forward and close the chair, the springs coil back up and the frame locks back into the original position.
Automatic models use an electrical source to power their internal motor. Pressing the button on an electronic recliner causes the the chair to slowly recline with power from the motor. Unlike lever-pulled models, electronic models aren't limited to a basic amount of positions--the reclining motion is fluid but can be paused at any time.
Lever-less models allow you to recline without using a lever. Leaning back on the chair pushes the frame back and allows you to recline. When you lean forward, the tension on the springs is relieved and they move back in place. This causes the chair to return to its original position.
Space-saving models allow you to place the reclining sofa flat against a wall. When you recline in a space-saving, or "wall-hugging" recliner, the back moves forward as the chair reclines, saving you valuable space.