How many types of khilaf (scholarly disagreement) are there and what causes it?

Summary

Khilaf is divided into two types: accepted khilaf (maqbul), such as the variations in types of hajj, and condemned khilaf (mazmum), caused by ignorance, injustice and extremism, following desires and conjecture, and contradicting the Prophetic methodology. Acceptable khilaf requires that it occurs among jurists, concerns branch and non-definitive matters, aims at seeking the truth, and involves genuine effort through ijtihad. Causes of khilaf include differences in understanding and command of knowledge, mastery of Arabic, the way fiqh sources are used as evidence, usuli principles, variant Quranic recitations and conflicting evidences.

Written in our own words from the original fatwa — check the source before acting on it.