What are the two different motivations for using spiritual texts like Guru biographies, as described in the preface?

According to the preface in Chapter 0, sacred texts such as Guru biographies and knowledge texts are used in two distinct ways. The first is 'Kamya,' which is undertaken with a specific desire, such as for worldly prosperity or for the removal of worries, calamities, distress, and diseases. The second approach is 'Nishkam,' which is done with a selfless mind for the ultimate purpose of liberation from the world and freedom from the cycle of birth and death. The text further clarifies that Nishkam Guru service is always considered superior.