Fardh is an
Arabic word. It is compulsory, necessary to perform. To leave it out is a large
sin. And Qaza (to redo it) is necessary. It means following Allah order. There
are 2 sides in Fardh, one of is called Fardh-e-Kifayah, and the other is
Fardh-e-Aiyn.
Fardh-e-Aiyn and Fardh-e-Kifayah
Fardh-e-Aiyn means you must do it for e.g. Salah, Ramadan (Sawm),
Zakah. And Hajj, Knowledge, men and woman should be separate. Fardh-e-Kifayah
means that if there are a few people and some of the people do it out all of
them, it is enough, not everyone has to do it then. For e.g. Janaza praying,
jihad, Islamic politics.