The verb "ser" is a fundamental Spanish verb that means "to be." It is used to describe essential characteristics, identity, and origin. For example, one might say "Ella es doctora" (She is a doctor) to indicate someone's profession or "Soy de México" (I am from Mexico) to express origin. "Ser" is an irregular verb, meaning it does not follow standard conjugation patterns. It is commonly used in the present tense, with forms like "soy" (I am), "eres" (you are), and "es" (he/she/it is). Understanding "ser" is crucial for effective communication in Spanish.