What is the difference between "ser" and "estar"

This is a very common question, so don't worry about it at all. So both verbs mean "to be", however we use them under different circumstances. As a general rule, "ser" is used for concrete, permanent characteristics. For example I am English and will always be English therefore "soy inglés".

Estar, on the other hand, is used for temporary conditions, things like emotions, moods or states. For example right now I am happy- "estoy contento", but yesterday I was sad- "estaba triste".

A good example which shows the difference quite clearly, is the word "nervioso" (nervous). If I say "soy nervioso" it means I am a nervous person, that being nervous is part of my character, whereas if I say "estoy nervioso", it means I am nervous right now, or I am feeling nervous (at this particular moment in time).