A split complementary color scheme is one where a primary color is used with the two analogous colors to its complement. In this case, blue is matched up with yellow and orange red. Orange is the direct complement to blue and orange red and yellow are the analogs to orange.
Split complementary colors have a strong visual contrast like standard complements, but tend to be a bit less jarring since they're not direct complements.
Splits also have the advantage of being a hard color set to mess up so they're good for those without much experience with color theory.