Semiotics, simply speaking, is the study of signs and how signs communicate meaning. It was first defined as a field of study with regard to language by Ferdinand de Saussure, a Swiss linguist. He looked at how words function as signs because they point to objects and concepts. We don't usually think about it, but when we say "cat," for instance, we usually mean the four-legged, purring, furry feline; and everyone else knows that, too, for the word cat is a sign that points to the creature in question.
Semiotics extends beyond language into the realms of visual, behavioral, cultural, and artistic signs as well. Think, for example, of the red octagon we so often see at intersections. Without even reading the word, we know that this sign means "stop." Signs are found in our body language as well. We understand that when a person nods, he or she is usually saying "yes." Even the tone, pitch, rate, and volume of our voices can serve as signs. We slightly raise the tone of our voice at the end of a phrase to indicate a question, for instance, and many people talk fast when they are nervous or loudly when they are upset.
Our culture provides us with a multitude of signs. A handshake indicates greeting or agreement. The image of a heart typically means love, as does a red rose. Artists, too, use a wide variety of signs to enhance their works. Painters focus on colors and shapes to depict meaning. Musicians use musical notations to indicate how their works are to be performed.
Indeed, signs are all around us, but they are so familiar that we rarely pay much attention to them. Semiotics works to raise our awareness of signs and to show how they create the meaning they communicate.