Transformer Power on the Primary and the Secondary
In an introductory book, the examples usually are very simple to make it easy to understand a new concept, so they migh only have loads that are resistive so there is no phase difference between current or voltage so they are not mentioned. Just like the transformer is assumed to be ideal with no losses.
There are no two loads as the ideal transformer does not itself consume any power, it simply allows power to be transmitted through it, but the transformer is able to transform the load impedance to be suitable with the provided supply voltage.
For example you have a 12VAC 1A load (say, a light bulb) but only 120VAC available (household mains in some countries). So the load is like a 12 ohm resistor that takes 12W, and it must be transformed to 12W load at 120V. Thus the voltage ratio is 10:1, and current ratio too. So via the transformer, it must look like a 0.1A load at 120V so it must look like like a 1200 ohm resistor as (10:1) squared is 100*12 ohms.