What is a deep well plate?

Deep well plates have many nomenclature variations, including microplate, microwell, and microtiter. A deep well plate is a flat plate that looks like a tray with multiple wells used as small test tubes. Well plates are typically mixed with 96,384 wells in a 2:3 rectangle, although other chamber configurations are available. Some other less common sizes are 6,24 wells. Although 96-well microplates are compatible with automated equipment, the 96-well format is the most commonly used well format because it can be used manually by laboratory technicians or researchers. A more common use of 96-well format microplates is in enzyme-linked immunosorbent assay technology. 

What are they used for?

Deep-well plates are used for a wide range of applications including cloning experiments, sample cultures, and in tissue culture-based assay systems