eActivity is the rewards programme for eCredits users. eActivities (ACT), the actual rewards, are not equivalent to eCredits, but they are earned for certain activities: For example, when you use eCredits for daily shopping or when you invite a friend to create an eCredits account, you are rewarded. The more you use the eWallet app, the more eActivities you earn.
eActivity is not a cryptocurrency, and eActivities are earned through being an active user of eCredits.