Spondylosis is arthritis that affects that spine. That's the simplest definition possible. Actually, looking at the Latin roots might give the simplest definition possible. Spondy means spine; losis means problem. Spondylosis, then, is a problem with your spine, but doctors today use it to specifically mean arthritis in the spine.
However, aging is an individual process. Just as some people go gray earlier, some people will feel the effects (mostly pain) of their aging spine earlier. In fact, some people may not have much pain ever. It all depends on how the parts of your spine are changing and if those changes are affecting the spinal cord or spinal nerves.
Spondylosis can affect all regions of the spine, another factor determining what symptoms you have. You can have spondylosis in your neck (cervical spine), mid-back (thoracic spine), or low back (lumbar spine).
You may hear spondylosis referred to by other names: spinal arthritis or spinal osteoarthritis.