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.

As the name implies, a coax signal splitter takes the power on the input port and splits it equally among the output ports.

For example, a 2-way splitter has one input port and two output ports.

It sends half the power of the input signal to one of the output ports. The other half is sent to the other output port.