The Difference between Teaching and Call to Action (Upadesa)

In Sankaradeva and Madhavadeva’s works, there are two components: one is the teaching and the other is the call to action. The latter is represented invariably in their works by a section called upadesa while the teaching is a broader aspect; it is the philosophical basis of the faith and of the system and indeed of the entire outlook on life that is suggested by the doctrine of eka sarana. This teaching seems to primarily revolve around the discrimination of the tattvas, the tattva viveka, via a description of the creation of the macro and microcosms by the supreme pure-personality and their evolution by His benign preserving influence. Of course, a puranic narrative is adopted in which these tattvas—the jada tattvas, as distinguished from the Lord—are dressed up in anthropomorphic garb and given the forms of personalities. This makes up a tale—a katha—in which the supreme pure-person is shown to direct, interact with, and, in the case of Krsna, even play with these personified forms; and His superiority to these forms is shown and further, the jivas are revealed not to be of the nature of these personalities—not the parts of matter—in actuality, but the parts, the amsas, as it were, of the Lord Himself.

In this manner, the teaching in its widest and broadest form, concentrates on explaining the evolution of the material universe in terms easily comprehensible to the lay listener; it is thus a teaching of the higher science imbued with a realization of the reality of pure-personality which aims to equip the student with a knowledge of the working of the highest material processes. It also contains knowledge of the transcendental society. This is the teaching in its most complete form.

The call to action or the upadesa, on the other hand, is the real call to action. Clearly, the knowledge acquired through the complete teaching is meaningless if we do not follow it up by the course of action or duty (dharma) suggested by it. Therefore, it focuses only on what the jiva should do. It cuts the waffle of theory and keeps only the cream of practical instruction. (In this sense, it also takes the teaching to its logical conclusion.) However, it does retain the minimum coating of theory required to give immediate impetus and an immediate rationale to the spiritual aspirant. Therefore, it would say that Krsna is the supreme pure personality, greater than all the remaining entities, but it would not enter into a prolonged description of ultimate reality, of the ontological categories. The objective is to bring only the final results of our scientific research to the populace and present to them only the fruit of it, the call to action suggested by it.
 

Simply by following this practical instruction given in the upadesa and with no grounding whatsoever in the theory of the teaching, the aspirant will obtain his highest joy and his supreme welfare. Nothing else is required. He can simply sing the names of ‘Rama’ and ‘Krsna’ taking sole-refuge in the Lord and obtain salvation effortlessly and with happiness; he need not know in detail the difference between jiva and Isvara.

[In marketing, a call to action (CTA) is an instruction to the audience to provoke an immediate response, usually using an imperative verb such as "call now…"
https://en.wikipedia.org/wiki/Call_to_Action]