When to create an array in memory and when to create in storage in Solidity?

Question

I was learning about arrays in Solidity . I am not getting exactly when should I create an array in memory and when in storage . So far I only know that an array created in memory is fixed in size and I cannot use push and pop methods in that case .

Can anyone explain the difference between an array created in memory ( what it is , how it behaves , gas costs etc . ) and an array created in storage ?

Reference : https://www.youtube.com/watch?v=vTxxCbwMPwo

Answer 1

The main differences are:

1. Storage, persistent contract state, costly
2. Memory, transient, fixed length only, cheaper

Generally, use storage to record things and memory as a scratch pad.

Hope it helps.