When do you use "ser" and when do you use "estar"
So "ser" and "estar" both mean "to be".Ser should be used when you're talking about an intrinsic quality of something eg. a description, the time, a characteristic of something - Miguel es muy divertido, Ya es las dos de la tarde etc.Estar should be used when you're talking about a mood or something non-permanent eg. location, feelings and moods, and when using the gerund - estoy al lado del parque, estoy enfermo, estoy disfrutando etc.
VG