Active voice is a grammatical construction where the subject of a sentence performs the action expressed by the verb. In active voice sentences, the subject typically comes before the verb, and the sentence structure is straightforward and direct. Active voice is often preferred in writing because it tends to be more concise, clear, and engaging for readers. For example, in the sentence "The cat chased the mouse," "the cat" is the subject performing the action of "chasing," making it an active voice sentence.