Every zodiac sign belongs to one of four elements. Understanding the elements is the fastest way to understand any chart — and any person.
Fire signs — Aries, Leo, Sagittarius — act first and feel their way forward. Earth signs — Taurus, Virgo, Capricorn — build, measure and maintain. Air signs — Gemini, Libra, Aquarius — think, talk and connect ideas. Water signs — Cancer, Scorpio, Pisces — absorb, intuit and remember. Twelve signs divide neatly into three of each, which is why every element has a recognisable personality signature regardless of which sign you are reading.
A chart rarely has one element only, and the interesting part is what is missing. Plenty of fire with no water reads as drive without emotional vocabulary; heavy earth with no air reads as practical but hard to move. Count the element of your sun, moon, rising and Mercury and you already have a usable sketch. The horizontal axis — how a sign operates — is covered under modalities, and the signs themselves under zodiac sign profiles.
None is stronger than the others — they are different tools. Fire moves fastest, air communicates best, earth lasts longest and water understands deepest. What people usually mean by a "strong" element is the one that dominates their own chart, which is a personal matter rather than a ranking.
You can have an imbalance, yes. Six or more placements in one element tends to over-develop that element's strengths and under-develop the opposite: too much fire burns out, too much earth stalls, too much air drifts into theory, too much water drowns in feeling. A little of the missing element usually balances it.
They share the names and the idea of four fundamental qualities, but astrology uses them as personality categories rather than as physics. The mapping to hot, cold, dry and moist comes from the same classical tradition, which is why fire is hot and dry while water is cold and moist.