They are dot/bar display drivers. You can select which mode, dot or bar, by how you wire it up. You can also get interesting combined effects, depending on how you wire it.
The LM3916 was designed to be a 10-LED VU meter display driver.
However, if you want to go to 12 LEDs, then use two of the LM3915 drivers, as the LM3916 does not work well when cascaded.
The way to find data sheets is to go to manufacturers website or sellers website and type in the part number in the search box. Parts that start with "LM" are made by National Semiconductors. My favorite site for data sheets is www.mouser.com because the search box jumps up on the first page at the top. Very easy to find.