Backcountry ski poles are generally lightweight and adjustable. When hiking uphill on a skin track, it’s nice to be able to shorten your poles to the length the terrain calls for. Once it’s time to ski downhill, adjustable poles can be reextended to the optimal length.
Because backcountry skiers spend a significant amount of time traveling uphill, minimal weight is a plus. As a result, most high-end backcountry ski poles are made from carbon fiber components. Additionally, some backcountry poles have a secondary grip that can be used to choke up on the pole when hiking uphill or traversing across a steep slope.
Resort ski poles tend to have a fixed length and are usually made from robust aluminum or bamboo.