À toutes et à tous

[Robert]

Is the expression 'à toutes et à tous' just a set phrase, or else is there some significant differences if one might put it simply:

À toutes

Or

À tous

[Vedas]

Hello,

It's the way to express that you address to both male and female people/audience.

toutes: feminine / plural

tous: masculine / plural

[Robert]

That's easy. Thanks

[Maurice O' Murchú]

On this point, if you were to say "bonjour a tous", would that not include both sexes?

[Maurice O' Murchú]

Correction, "bonjour à tous".

[Vedas]

It would generally but depending on  circumstances political correctness or politeness wants it that you address to both sexes differently.

For instance anytime the French president delivers a speech on TV he would start it  with "(chèrs) Français, (chères) Françaises just like ladies and gentlemen...