Spinal fusion is a big surgery to connect two or maybe more vertebrae in your spine then there is no motion at all between the vertebrae. Spinal fusion puts extra bone or metal in to fill space between the vertebrae. After the surgery it is fused and there is not movement there at all. This surgery is usually performed along with another surgery at the same time for example: a diskectomy or laminectomy. They will use general anesthesia for this surgery and you will not be awake while it is being done.
This is normally a big surgery that takes a couple of hours to perform. It is also a quite expensive surgery. You will normally use your own bone or a metal implant depeneding on the surgeon and your underlying problem. The surgeon may use plates, screws, or rods to hold vertebrae and for healing after the fusion. There is usually a long recovery with this surgery.
Complications that may occur with this surgery are: pain where the surgery was done, bleeding, blood clots, infection, poor healing, injury to nerves. Spinal fusion is typically an effective surgery. After the surgery you are fused in that spot and it does not move the same way as it used to. There is no way to predict if it will take all or most of your chronic pain away.
You may be a fairly good candidate for fusion if you have chronic low back pain, broken vertebrae, spinal deformity or spinal weakness. The surgery is usually safe. But as with any surgery the benefits and risks should be discussed before committing to this surgery. Also you may want a second opinion before agreeing to it.