Tone:quality or character of sound.

key:the relationship perceived between all tones in a given unit of music and a single tone or a keynote;tonality.

Note:a sign or character used to represent a tone,its position and form indicating the pitch and duration of the note.

but basically,the relationship between them is that tones make up notes which make up keys.

tones are the sounds that we receive individually-pitches,if you will.

Notes are those pitches with names.when we actually divide them up into individual sounds that we name and can  record.the keys in the piano or the strings of a violin, etc.

Keys are when we put the notes together into a sequence.there are many different combinations that people have put together over the years,but basically it's a group of notes in a row.