Overall, the Chariot is essentially about balance. We see it expressed with various depictions within the card: two sets of castle towers, two wheels on the chariot, the uniting of positive (masculine) and negative (feminine) energies with the Shiva Lingam-like symbol on the shield, the two wings, the three trees on either side of the chariot, the two crescent Moons that reflect the sign of Cancer, as well as the two sphinxes. The Chariot’s numerology of seven also implies balance, in that the number seven can depict a scale with its two pans.
That said, I typically interpret The Chariot as knowing when to assert control and when to drop resistance, which is another way of saying, balancing projective with receptive presence, self-assertion with observation, or action with rest. The square glyph for Elemental Earth appears on the King’s breastplate, suggesting groundedness as an expression of balance, as do the four poles that support the Merkaba-like stars in the canopy above. The two lions/sphinxes represent the balance between the masculine and feminine within. And a note about the Merkaba-like stars. They too describe the merging of the soul with physical reality and the as above, so below balance that flows through our lives.
When The Chariot appears in a reading, it suggests knowing when to take control and assert yourself and when to step back and observe. It suggests a level of mastery that needs no assertion and trusting your own process.