How would you detect if a player has said "hello" in a message (onChatted) , even if the message isn't only "hello" and is somthing more like "hello friend" without actually doing somthing like if message == "hello friend" then, ect..
You'd use string.find, a way to find if a selection is in a string.
player.Chatted:connect(function(chat) if chat:find("hello") then -- do stuff end end)
Look up strings on the ROBLOX wiki for a whole load of more useful string related functions