Wikipedia
Riving knife
A riving knife is a safety device installed on a table saw, circular saw, or radial arm saw used for woodworking. Attached to the saw's arbor, it is fixed relative to the blade and moves with it as blade depth is adjusted.
A splitter is a similar device attached to a trunion on the far side of the saw and fixed in relation to the saw table, which must be removed to make any non-through cuts or dados within the depth of the wood.