In order to call a beer a "fresh hop" it must be brewed using hops that are less than 24 hours off the bine (a climbing plant that climbs by its shoots growing in a helix around a support, in contrast to vines, which climb using tendrils or suckers). This happens only once a year.
Hops are ready to harvest when the moisture level in the cones reach a certain level, typically around 80 percent. The length of the days and nights dictates when hops are ready for harvest. That is why hops come ready at the same time every year...end of August through September.
Why do we like fresh hop beers? In the end, you get a beer that some say has a bright, fresh hop flavor that is unlike beer brewed with processed hops. So most brewers opt to make a lighter-bodied ale from the fresh hops.
I have heard that some people think fresh hop beers are a bunch of hooey. They think it is just something to get beer drinkers excited and consider fresh hop beer to be a gimmick. I am not one of those people. I love fresh hop beer, not just for the taste, but for what it represents. It is a liquid celebration of the annual hop harvest! Right??