Left & right side dominance
The brain's right hemisphere controls the muscles on the left side of the body. The right hemisphere is mainly in charge of spatial abilities, face recognition & processing music. The brain's right side also help us to comprehend visual imagery & make sense of what we see. It performs math but only rough estimations & comparisons.
The brain's left hemisphere controls the muscles on the right side of the body. The left side is dominant in language, processing what we hear & handles most of the duties of speaking. It is in charge of carrying out logic & exact mathematical computations. When we need to retrieve a fact, our left side pulls it from our memory.
To see which side I use more I took 2 brain dominance quizzes. On the first quiz my results were that I used more my left side, having 53% on the left side & 47% on the right side. On the second quiz my results were that I responded 8 questions as a right brained person & 11 as a left brained, so according to both quizzes I use more my left side.