An active sentence has the word order -- subject + verb + object. In an active sentence you can see who does the action. eg -- The dog chased the cat. (the dog does the action)In a passive sentence the word order is -- object + verb. The person or thing that does the action (agent) is not necessarily given eg -- The cat was chasedIf you want to say who or what did the action in a passive sentence you add it at the end -- by + noun/noun phraseeg -- The cat was chased by the dog. or The cat was chased by a pack of dogsPassive sentences are often used if you a writing about a process, where who or what does the action is not important. eg Tea is grown in China. It is processed and is packed in boxes.Or other sentences where the agent is not known. eg The Mona Lisa was painted around 1503.Or if the agent is the most important piece of information. eg The painting was painted by Van GoghA passive sentence verb has the form -- be + past participle eg was chased, were chased, is being chased, had been chasedetc