Active voice is a grammatical voice common in many of the world's languages. It is the unmarked voice for clauses featuring a transitive verb in nominative accusative languages, including English and most other Indo-European languages. Active voice is used in a clause whose subject expresses the agent of the main verb. That is, the subject does the action designated by the verb.
For Example :
1. I buy a book today
2. I shall visit my father tomorrow morning