Gemini is symbolized by the Twins, and ruled by Mercury. This makes Gemini a dual sign, one with two sides.
This means that wherever you have Gemini in your natal chart, that area is one where you may find you're split in two. You have "two" in some way - sometimes very literally!
Gemini is an air sign, along with Libra and Aquarius. The air signs are the signs of the mind, intellectual and sociable, and aware of the moving times. These signs can weigh options and have varied opinions.
Gemini is also a mutable sign, along with Virgo, Sagittarius, and Pisces. The mutable signs are the ones that flow. They ebb and flow, come and go. They're highly adaptable and flexible, so they can start one way and go another very easily.
Gemini is ruled by the planet Mercury, who is always going, always thinking, always on the move. Mercury is a fast planet who can cover lots of terrain, and this helps Gemini to manage its dual nature.
So, Gemini is a sign that is moving constantly, has varied perspectives, and has a strong dual nature. The areas of life ruled by the house in your natal chart that falls in Gemini gets this energy.
Suggested Reading: Aquarius Houses: Where You're Different