A piano has approximately 220 to 230 strings, and Piano Tuning is an art of turning the pins of the strings' tension to get the piano into producing a clear and perfect tone.
Shifting or moving the piano, humidity changes as well as extraordinary playing can cause the piano to go out of tune.
Piano that has not been tuned regularly can become flat or sharp in its tonal quality.
To prevent all this from happening, it is advisable to have two or more thorough tunings in order to raise the piano pitch to international standard. Normally, home pianos need to be tuned at least once a year but twice is recommended for better performance.
Tuning is an art practiced by skilled professionals and under no circumstances should anyone other than a professional technician be allowed to tune your piano.