Okay kiddo, so you know when people talk or write, they use different ways to say things. One way is called the passive voice, where the thing receiving the action is the subject of the sentence. For example, "The dog was walked by John."
Now, the antipassive voice is when the sentence is changed so that the thing doing the action becomes the subject, and the thing receiving the action is not mentioned. For example, "John walked the dog."
It's like playing a game of "who did it?" but instead of focusing on who the action affected, we focus on who did the action. This way of speaking or writing is used in some languages more than others, but it's not as common as the passive or active voice.
So, the antipassive voice is just another way to talk or write where we focus on who did the action instead of who or what it affected.