• identity of person, thing, event
• occupation or profession
• unchanging qualities (nationality, morals, religion)
• characteristic or physical appearance or personality
• relationships
• time
• place and date of an event
• origin, possession, materials objects are made of
• quantity and price
• passive voice (ser + participle + por)
• impersonal expressions

Estar:

• locations
• temporary physical conditions
• temporary mental conditions and moods
• temporary traits or qualitie
• suse with preposition de
• use with gerunds (-ando, -iendo)