Piano sheet music is written music arranged for piano. Typically a piano sheet will also include basic chord information for other instruments. Simplified piano music may include chord indications for the pianist who isn't quite up to reading music well enough to recognise chords on the staff. There are three basic ways chords can be notated in piano music. Learning to recognise and understand these chord notations isn't difficult and can improve your ability to sight read piano sheet music.
Look for the chords on the music staff. Three or more music notes written together indicate a chord is being played. Look at the lowest note of the chord. This is most often the root name of the chord. There are many variations of chords and chord voicings, so purchasing a chord theory book to keep handy until you're familiar with how chords are constructed is something to consider.
Read chord symbols written in letter and number form to see chord changes in the piano sheet music. These letter and number combinations include C, Csus, Caug, Cm and C7. Again, a basic understanding of chord structure will be helpful. C tells you to make a C major chord, Csus tells you to play a suspended chord (replace the third note of the scale with the fourth), and C7 tells you to play a seventh chord.
Read chords from guitar chord diagrams found in piano/guitar sheets. These diagrams are written above the staff and resemble the neck of the guitar, with lines representing the strings and black dots on the lines to show a guitar player how to finger the chord. The diagrams themselves are not normally useful to a piano player except when the chord name accompanies the diagram, or if the piano player is also a guitar player.
Purchase a book on chord theory. It can take some time to gain an understanding of how chords are structured, so having a book on hand that shows piano fingerings for chords and explains how chords are built can improve your chord notation recognition.