Rajas is a fundamental concept in the Mahabharata and, more specifically, the 18 chapters of the Bhagavad Gita nestled within it. The concept transcends mere characterization and signifies one of the three modes of material nature, according to Hindu philosophy. These three modes, or gunas, are Sattva (goodness, constructive, harmonious), Rajas (passion, active, confused), and Tamas (darkness, destructive, chaotic).

In the Bhagavad Gita, Rajas represents passion, activity, and desire. It's one of the influencing factors in our lives, driving us toward action, ambition, and worldly development. Like the other gunas, it's intricately woven into the fabric of everyone's existence, constantly shaping behaviors, thoughts, and emotions.

Rajas is not inherently bad, but its association with constant thirst for action and unfulfilled desires can lead to restlessness, dissatisfaction, and imbalance. It is intricately linked with the idea of karma because it often spurs humans into action, thus triggering the law of cause and effect.

This mode of material nature is also closely tied with the performance of duties and responsibilities, both in personal and social contexts. Rajas-driven actions often seek tangible, immediate results and thus can result in attachment to those outcomes.

To achieve spiritual advancement and peace in life, the Bhagavad Gita recommends transcending these modes, including Rajas, to reach a state of equanimity, where actions are performed with detachment from their results.

Therefore, 'Rajas' can be seen as a vital energy that fuels ambition and action but needs to be balanced to prevent dissatisfaction and restlessness. It's a powerful component of human nature, contributing greatly to progress and change, but can also trigger disquiet and imbalance if not wisely managed.

While talking about 'Rajas' in a secular language, it can be understood as an inner force driving our passion and desire for achievement but also causing restlessness if results are not as anticipated. In essence, finding a balance and transcending this force is the key to inner peace and fulfilment, as highlighted in Hindu philosophy and outlined in the Bhagavad Gita.