1-I'tikaaf is to be in seclusion for the purpose of worship.
2-It is a kind of worship done only in the masjid (mosque).
3-Doing it in one of the three mosques earns more reward.
4-Its ruling is Sunnah not waajib.
5-But it becomes waajib(compulsory) if one vows to.
6-Al-'itikāf is done at any time of the day or the night of any month.
7-Full-day, half-day, an hour or less counts on the I'tikaaf.