"New Leather" is a name given to the more recent style of BDSM practice and communities, and is used in contrast to "Old Leather," which began in the 1940s and is, arguably, the precursor to all modern BDSM communities. New Leather is less formal, more individualistic, more casually social and relies less on hierarchies and formal training.
More About New Leather
The name New Leather, also known as New Guard, is used to describe people who participate in the leather community, but who don't follow the strict rules and hierarchies of the Old Guard communities.
This, according to experts and members of the community, happened because of greater commercialization and acceptance by the wider public, as well as larger numbers of people participating in BDSM who do not necessarily want to engage with the leather subculture. (BDSM and the leather subculture are linked, but one does not always follow the other.)
In fact, some writers argue that the two tendencies---one towards militaristic-style hierarchy and protocol, and one more individualistic and free-form, have existed since the beginning of the leather subculture itself, in the biker clubs of post-WWII.
So "New Leather" might not be so new after all, but there might be enough participants nowadays to give an official name to something that had existed all along.