Janaretoci na'urori ne na injiniya waɗanda ke canza wasu nau'ikan makamashi zuwa makamashin lantarki. Ana tura su ta hanyar injin turbin ruwa, injin turbin tururi, injin dizal ko wasu injinan wutar lantarki kuma suna canza makamashin da kwararar ruwa, kwararar iska, konewar mai ko fashewar nukiliya ke samarwa zuwa makamashin injiniya wanda aka mayar da shi ga janareta, wanda aka mayar da shi makamashin lantarki.
Ana amfani da janareto sosai a fannin samar da masana'antu da noma, tsaron ƙasa, kimiyya da fasaha da kuma rayuwar yau da kullum. Janareto yana zuwa ta hanyoyi daban-daban, amma ƙa'idodin aikinsu sun dogara ne akan dokar shigar da lantarki ta hanyar lantarki da kuma dokar ƙarfin lantarki. Saboda haka, babban ƙa'idar gina shi ita ce: tare da kayan maganadisu da masu sarrafa su don samar da da'irar maganadisu da da'irar maganadisu, don samar da wutar lantarki ta hanyar lantarki, don cimma manufar canza makamashi. Janareto yawanci yana ƙunshe da stator, rotor, ƙarshen murfin da bearing.
Stator ɗin ya ƙunshi tsakiyar stator, naɗewar naɗe waya, firam ɗin da sauran sassan tsarin da ke gyara waɗannan sassan.
Na'urar rotor ta ƙunshi abin juyawa na tsakiya na rotor (ko sandar maganadisu, mannewar maganadisu), zoben tsaro, zoben tsakiya, zoben zamewa, fanka da kuma matse mai juyawa, da sauransu.
Murfin ɗaukar kaya da ƙarshen zai zama stator na janareta, an haɗa rotor tare, don rotor ya iya juyawa a cikin stator, ya yi motsi na yanke layin maganadisu na ƙarfi, don haka samar da damar shigarwa, ta hanyar jagorar ƙarshe, wanda aka haɗa a cikin madauki, zai samar da wutar lantarki
