If I play a F# for example on my A string, thats still the same if I played a F# on the E string? It sounds different obviously. What about piano? I F# on piano is the same as guitar?
yeah but there are different octaves, same note, only higher.

if you play the second fret on the E string (F#), you can play the 9th fret on the A string which is also an F#, but it's higher. and yes, if you played an F# on the piano, it would be the same pitch as on the guitar.
Quote by pepsi1187
notes are the same on any instrument

Sort of. Guitars, pianos, xylophones and similiar instruments would be the same, as they're based on C. Trumpets are based on Bb, alto saxes in Eb, and such. So you could play the same note, but they would have different names.
Quote by terryguitar

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Ummm, petrol? Nip down to your local petrol station, buy a litre of the stuff and soak your balls in it, light them up and start playing with them.
depending on what string you play, you may find you get some minorly different tonal qualities even though you are playing an identical note.

Notes are universal though (at least in concert pitch)... there are octaves of pitches which will be higher or lower. But yes... playing a C on a piano and a C on a guitar will be the same note... depending on the octave.