People use sheet music to play the piano. Each note on the sheet music is a key on the piano. Each key should be held for a certain amount of time depending on the type of note is on the music sheet. Some notes are played together at the same time. If the notes are in a vertical line together on the sheet music, then those notes will be played at the same time.
On the piano, the main note is called middle C. This key is in the very center of the keys. Then there are other lettered keys around middle C. These are the white keys. There are also black keys called sharps. Sometimes, these are played with the white keys.