Here are the Jain meanings of Upayog (upayoga) in simple terms:

• Core meaning in Jainism: Upayog means the soul’s active use or attentiveness of its own cognition. It is the soul’s ability to think, perceive, and know things through its inner faculties. In short: attentive consciousness and the exercise of knowledge and perception. (This is the primary sense found in Jain scriptures and commentaries.) ( jainknowledge.com)

• Two main types of upayog (cognitive function):

- Darśanopayog: the function of perception (seeing, sensing). - Jñānopayog: the function of knowledge (understanding, remembering, reasoning). These together describe how the soul cognizes objects. ( jainknowledge.com, jaincosmos.blogspot.com)

• A more technical Jain definition: upayog is the manifestation or activity of consciousness; it is the basic attribute by which the soul cognizes and experiences. It can be pure (undefiled) in a liberated state or impure in a bonded state due to passions. This helps explain why some upayog binds karmas and some frees the soul. ( jainqq.org)

• A broader usage you may hear: in ordinary language, upayog can also mean usefulness or utility. In Jain texts, however, the above spiritual sense of attentive cognition and its manifestations is the primary meaning.

Note on tradition differences:

• The core concept (attentive cognition of the soul) is shared across Digambar and Śvetambar sources. Some texts emphasize the twofold aspect (darsanopayog and jñānopayog) and discuss purity/impurity of upayog, but the basic idea remains the same in both traditions.

You can read more in these Jain-focused discussions:

• The Theory of Knowledge in Jainism (discussion of upayoga as a cognitive function).
• The Three Jewels of Jainism (context where upayoga is mentioned as part of knowledge/perception discussions).