Answer:
Ser is used to describe what a noun is.
Step-by-step explanation:
In Spanish, the verb "to be" has two meanings, ser, and estar.
We use ser, to talk about what a noun is, it is used to talk about permanent states, such as characteristics. For example, we can say, La casa es grande (the house is big) or Ella es Sally (she is Sally).
We use estar, to talk about how a noun is, it is used to talk about temporary states because we are referring to temporal feelings, actions, conditions, etc. For example, we can say, El gato está debajo de la mesa (the cat is under the table) or Ella está feliz (she is happy).