"Dude" is a word that tons of people use for tons of things. Anyone can be called "dude", even if you are a girl. It can be used in so many many ways in so many situations and it can still make sense.
"Hey, dude, wassup?"
"Dude, that was so awesome!"
"Duuuude!"
(and there are infinite other examples)
A term used mostly by teens and nineyear old kids.
Killame the nine year old : Dude! I found a cool blue and green color rock!
Jiffa the nine year old : Really Dude! Oh my gosh show me!
James the teenager : Dude, you wanna game it out today?
Jeffrey the teenager : Naw dude, I ain't feelin' it today
James the teenager : Alright dude, imma leave then
Now you probably saw the difference between a teenager using the word "Dude" and a nine year old kid using the word "Dude."