A counter expression meaning six long cylindrical or stick-like objects (e.g., six bottles, six pencils).
ビールが六本入っています。
There are six bottles of beer.
机の上に鉛筆が六本並んでいる。
Six pencils are lined up on the desk.
誕生日に父にバラを六本買ってあげた。
I bought six roses for my father on his birthday.