weird professional cameras

[Dwig]

s... i think it was a twin lense that is what i saw on b&h. what do they do special

If what you saw looks like these:

Rolleiflex - Camerapedia.org

then they were some model of a TLR (Twin Lens Reflex). These were a very common style of camera with pros and serious amateurs between WWII and the mid to late 60's.

The design was a compromise between a SLR (Single Lens Reflex) and a simple VF (View Finder) camera. They gave a close to the same viewing accuracy as an SLR without the SLR's complex, heavy, and vibration producing moving mirror. Also, at the time of the birth of the TLR (roughly the early 1920s) SLRs didn't have mirrors that returned to the down position after the shot so their VF's when black until you recocked the shutter, lens aperture, and mirror (often three separate steps and separate from the film wind). The TLR was an elegant and simple design by comparison.

It wasn't until the mid-50's that the SLR design had evolved enough to begin to compete against the VF and TLR styles for most use. Despite the fact that SLR cameras first appeared in the late 19th century and were, in the form of the Graflex models in 2 1/4 x 3 1/4 to 5x7 sizes which were solid mainstream professional cameras, SLRs were not viable as work-a-day pro cameras when smaller format eclipsed the old sheet and filmpack sizes. The first truly modern SLR containing all of the needed advancements to compete in a modern professional arena didn't appear until 1959 with the introduction of the Nikon F.