Iddah has different types:
1. Iddah after divorce (عدة الطلاق) which is must after a woman is divorced from her husband. It takes three months of less depending on three menstrual periods if she is not pregnant and if she is pregnant, then her Iddah will continue till she delivers her child. Iddah of Talaq must be observed in the matrimonial house. It is not allowed for the husband to drive her away, nor she is allowed to leave matrimonial home.
(O Prophet, when you divorce women, divorce them according to their Iddah, and count the Iddah, and fear Allah your Lord. Do not turn them out of the homes of their homes, not shall they leave) (Sura Al-Talaq, verse 1).
2. Iddah after husband's demise (Iddah Wafat) which is four months and ten days during which she must observe mourning and not take part in any celebration or happy event, nor wear colorful dress.
She can observe this Iddah of Wafat in her home or any other safe place where she observes full Hijab with mourning.