As the Earth orbits, the position of the sun among the stars appears to change each day. If you traced this path day-to-day throughout the year, it would make a line across the sky. We call this path the ecliptic. The sun appears to move, but this is really caused by the motion of the Earth around the Sun. Thus the appearance of the sun at any particular point of the ecliptic occurs on about the same date each year.
You can make the same observations for the planets. Trace their positions among the stars day-to-day all year. Their paths do not line up exactly with the sun, but will be very close. The Zodiac is a band of sky wide enough to contain the orbital paths of all the planets. It extends 8-9 degrees north and south of the ecliptic in the sky.
There are 12 constellations famously known as the “Signs of the Zodiac”, but in fact pieces of many constellations extend into the Zodiac and some of their stars will appear as potential stars of your birth.