Imagine that your brain is a store cupboard. 'Retain' is what you keep in that cupboard. 'Recall' is what you bring out and use.

retain is to keep and conserve something, for example, your possession recall is to bring out or remember some memories that had happened a long time ago, for example, recalling your childhood friends and memories

Retain :- continue to have (something )keep possetion of. Recall :- to bring the memory of a past event in to your mind, often to give adescription of what you remember.