It is the conjugation of the verb "avoir" (to have) in the third person singular feminine present tense.
Here are some examples:
* Elle a un chat. (She has a cat.)
* Elle a 20 ans. (She is 20 years old.)
* Elle a faim. (She is hungry.)
"Elle a" can also be used with adjectives to describe someone's state or condition:
* Elle a peur. (She is afraid.)
* Elle a froid. (She is cold.)
* Elle a raison. (She is right.)