Conditions, Pillars, Obligations, and Recommendations of Salah:
• Conditions (Shurut): These are the prerequisites that need to be present before entering the Salah and maintained throughout the Salah till the end. This is unlike the pillars where one moves from one pillar to the other.
• Pillars (Arkan): The actions that are inside the Salah, which cannot be left out intentionally, nor out of ignorance, nor out of forgetfulness.
• Obligations (Wajibat): The actions that are inside the Salah, which cannot be left out intentionally, but is dropped if one does so out of forgetfulness or ignorance; one then is required to perform the two prostrations of forgetfulness at the end.
• Recommendations (Mustahabbat/Sunan): These are also actions that are inside the Salah. However, the Salah is still valid if one leaves them out, intentionally or unintentionally.