Explicit consent - is an expressly confirmed type of consent. You have to confirm you agree with something or give a permission to do something. For example, in displayed pop-up, user have to confirm that he agrees with online call recording, by clicking on "Yes".
Implied consent - is an indirect consent, granted by user's action or inaction. For example, user can see the notification, that online call is recorded. If he stays on the call, he agrees with recording.
The definition of explicit and implied consent may vary on jurisdictions. The usage of implied consent may be more or less limited in some countries.