A piano will eventually reach the point that it needs reconditioning in order to remain viable as an instrument. The alternatives being: to keep it purely as piece of furniture or scrapping it.
The amount of work required can vary widely. Sometimes reconditioning the Action (the unit that contains the majority of moving parts), is enough. Typically this would mean replacing or re-facing hammer heads, replacing any other felts, leathers or springs that are worn, and replacing the pins that pivot the moving parts: re-centering. Regulating, tuning and voicing would add the finishing touches.
Other pianos may require more extensive work, more often referred to as Re-building. This may involve re-stringing, repairs to the soundboard, re-bushing of keys and attention to the casework, as well as the work already listed above.
If you are considering giving your piano a new lease of life, please contact me. I can arrange to inspect the instrument, and if I feel that the piano would benefit from this level of work, advise of the best way forward.