As the first patent in this list, it may seem insignificant. However even this one opens the door to many others in an orderly progression. Notice how all the patents with similar titles build on each other. One of the most interesting aspects of Tesla's patents in general is that they don't become obsolete. An older patent may still be useful in terms of building something when materials are limited, or when integration with older components is necessary.

Primarily this patent was intended to resolve the problem of sparking as motors were spinning. The commutator is what passes electrical current from a rotating part into electric wires.

Significant quote from the patent:
"My invention enables me to prevent the sparking in a simple manner. For this purpose I employ with the commutator-bars and intervening insulating material mica, asbestus paper or other insulating and preferably incombustible material, which I arrange to bear on the surface of the commutator, near to and behind the brush."

Note how Tesla provides options for the use of several different materials. This stands in sharp contrast to many of Edison's inventions, which often depended on exact material compositions.