‘tan’ means “elaborate on, expand on”, and ‘tra’ means “save, protect”. So Tantra is a Divine practice that saves through expansion. ‘tra’ is also translated as ‘tool’ (like mantra - mind tool), so Tantra can also be considered ‘a tool of expansion’.
In order to have this living experience, infinite consciousness condenses itself into limited individual consciousness (Soul) and form (matter). In doing so, infinite consciousness willingly obscures itself to complete truth - it forgets everything it knew. Then, as we develop, we expand our conscious knowledge through learning not by adding, but by revealing something we’d known but forgotten.
By expanding our consciousness we take ourselves in the direction of infinite consciousness - returning to the Divine. Everything we know will only ever tend to zero compared to the vastness of everything we don’t know, but even an awareness of that is itself expansion, and so positive. This means our expansion into the Divine isn’t necessarily to be found in the knowledge, but in the awareness.
Tantra saves us by providing practices that allow the awareness of expansion/expansion of awareness (such as yoga, meditation, mantra, yantra, study, ritual), enabling us to learn to be present, thereby returning to a blissful state from which we can then find worldly enjoyment.
Simply put, Tantra is a Divine system to help you reveal your best self and enjoy your best life.