As the name implies RF power splitters / dividers and combiners are used to split a single RF line into more than one line and divide the power, and similarly combiners are used to combine more than one feed line into a single one.
RF power combiners and RF splitters are the same items. The same circuits can be used to combine and split RF power, the only difference being that RF power is applied to one port and extracted from other in the case of the RF splitter, and for the RF combiner, power is applied in the opposite direction.