To explain tone and timbre, if we produce a 2000 hz note on a guitar and a piano, then the harmonics associated with that note, which help us distinguish if it is a guitar or a piano is called as Timbre. It is usually associated with the aftertones of a tone, like the decay or harmonic structure, that help us identify the exact instrument playing it.
Coming to the tone itself, it is referred to the exact pitch of that note. The pitch of every note can be considered as a combination of the lower section ( say bass ) and the higher section ( say treble ). When we change tone control on a amplified signal, the pitch changes with the frequency being the same. For example, we can lower the tone control on a guitar amp and it will sound more heavy and bassy. Increasing the tone, will make it more lean and bright. And both the above pitches, are generated from the same guitar at the same frequency.
Thus, different types of guitars, producing the same note can sound different, due to differences in pitch, which we call as tone. And difference between a guitar and a violin or a piano at the same frequency note is timbre. Though usually, both the terms are used in conjunction, to associate how accurate the reproduction of a instrument on a system is. And the ability to distinguish a complex musical passage, with several similar instruments playing at very close frequencies is called as texture. That is getting a combination of tone, texture and separation right.