The verbs 'ser' and 'estar' both translate to the English 'to be'. But don't worry! There are some key differences that help us know which Spanish verb we should use. 'Ser' is used to describe permanent characteristics - the ESSENCE of the thing or person we are talking about. We use 'ser' when for: DESCRIPTIONS (names, physical descriptions, nationalities, religion), OCCUPATIONS (jobs, hobbies), CHARACTERISTICS (personality descriptions), TIME (hour, day, date, year), ORIGIN (place person or thing is from, material something is made of), and RELATIONSHIPS (family ties, friendships, romantic relationships).
'Estar' is used to describe TEMPORARY STATES and locations. We use 'estar' for: POSITIONS (physical position or posture), LOCATIONS (permanent, temporary or conceptual - N.B. the exception for the location of events or parties, for which we use 'ser'), ACTIONS (ongoing actions, usually followed by a present participle, e.g. 'lavando' or past participle, e.g. 'muerto'), CONDITIONS (temporary mental or physical, lasting hours, days or even years), and EMOTIONS (how a person is feeling at a certain moment).