Polina's link is perfect. In short the difference between the two is : Active : The subject PERFORMS an action on the object Passive : An action IS PERFORMED by the subject on the object Both mean the same thing, just said in a different way. Active : Tom CATCHES Jerry Passive : Jerry IS CAUGHT by Tom :)

http://www.native-english.ru/grammar/passive-voice По-русски это не пассивный, а страдательный залог. Миша прочитал книгу - активный залог. Книга была прочитана Мишей - страдательный залог.