You do know about it - it is generally shortened to just "fardh". Meaning obligatory. the "ain" bit means on the "one" or individual, so "fardhul ain" is "personal obligation" - something that is obligatory on an individual level.

There are two times of obligations - personal obligations and communal obligations.

A personal obligation is the one that you know everything about - praying, eating halaal food etc, earning a halaal wage, fasting in ramadan, doing the hajj once in a lifetime etc etc.

With personal obligations, it is a sin to not carry them out.

A communal obligation (known as fardh kifayah, or fardhul kifayah in arabic) is one where there is no personal obligation or sin unless no one stands up and does what is required.

An example of this is the funeral prayer - it is "fardh", but a communal one, meaning that as long as someone turns up to the funeral prayer, the whole community is not sinning. But if no one turns up, then it is a sin.

Preaching is given a similar standing - it is obligatory to preach about Islam, but at the same time not everyone has to go out and do it. As long as there is someone in the community doing the preaching, there is no sin to anyone else who is not doing it.

(on another level, a community needs a doctor, but everyone does not need to become the said doctor...)

And now I know what 'Fardhu ain' means.

In the Communal obligation; who takes the sin for that one person not turning up? Everybody?

s.b.f wrote:

In the Communal obligation; who takes the sin for that one person not turning up? Everybody?

yes. But if someone does fulfil the communal obligation, if others do not help, there is no sin (no reward either - that goes to whoever acted).