Pokéflute is the key item in Pokémon FireRed and LeafGreen.It is given to player by Mr.Fuji at the Pokémon Tower in Lavender Town.
Story Line Use
In the main story line,Pokéflute was used for waking up the snorlax who was blocking the way to Fuchsia City.Another Snorlax who is also making the way uncrossable to Fuchsia City is also awaken by Pokéflute.
In Battle Use
In the battle it can be used to wake up a sleeping Pokémon.