having a repeated concept one time

Hi Guys,

I have this information in column A, the information is repeated and what I
want to have a second column with the information just ones, but I need this
to be synchronized, as soon the user include a new concept in column A I want
that concept in column B, if include a concept that already exist nothing
happen because is already in column B, I don’t want the users to go thru
filter option.

I would really appreciate if someone can give me a hand with this.

Thanks



Column A Column B
Plane Plane
car car
moto moto
bici bici
moto Truck
truck skii
truck
skii
truck
skii
truck
truck