Internal is with yourself, I.E. trying to decide which phone to get. External is when you have conflict outside of the mind such as an argument with someone. Basically: Internal: Self and mind External: Society and man
External conflict is something outside of a person. Internal is inside. Example: external conflict would be like the character has to fight a dragon to escape. Internal would be like the person hurt themselves
An internal conflict is something that occurs within you, for example: a boy deals with the loss of his dog. His sadness is the internal conflict. An external conflict can be an external power against you (that probably isn't the best explanation for external conflict). Example: a bully picks on a boy. The bully is the external conflict.