بسم الله الرحمن الرحيم
(Fatwa: 699/722/L=06/1436)
(1&2) What you heard is right. Slandering and backbiting is haram. Backbiting is to speak of a person in his absence what he will dislike if hears it, even if it is true. Backbiting whether between spouses or someone else is haram in each case. It should be noted that as backbiting is done through tongue in the same way it is also done by gesture i.e. instead of uttering bad words, making a wrong gesture is also backbiting.
قال فى الدر المختار: وفيها: الغيبة أن تصف أخاك حال كونه غائباً بوصفِ يكرھه إذا سمعه ……. وقال قبله وكما تكون الغيبة باللسان صريحاً تكون ايضاً بالفعل وبالتعريض وبالكتابة وبالحركة وبالرمز بغمز العين والإشارة باليد وكل ما يفهم منه المقصود فهو داخل فى الغيبة وهو حرام (در مختار مع الشامى 9/587)
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband