More is not always better, as we shall see. A decibel is one tenth of a Bel. 10 dB equals a Bel, but we never call it a Bel. The Bel, by the way, was named for Alexander Graham Bell. Decibels are not an absolute measurement by themselves.
Decibels are a relative measurement.
Antennas are rated by dB gain. We can use some analogies to help us understand. Picture a sphere, or sort of like a basketball, stuck down over your antenna. This basketball represents the coverage pattern of a unity gain antenna. Most handheld radio antennas, and some mobiles, are of this type.