Apart from and except for are multi-word prepositions. Apart from can mean either ‘including’ or ‘excluding’: Apart from Germany, they also visited Italy and Austria. (including Germany, in addition to Germany) I like all vegetables apart from tomatoes. (excluding tomatoes) Apart from Friday, I’ll be in London. (excluding Friday) Except for or except only mean ‘not including’ or ‘excluding’: I like all vegetables except for tomatoes. (excluding tomatoes) Except for Jim, who is unwell, they are all ready to leave for America tomorrow. She enjoys all sports except swimming. source: https://www.google.com/amp/s/dictionary.cambridge.org/amp/british-grammar/apart-from-or-except-for hope this helps. :)

Sara is right in saying that they are interchangeable, but there are examples when they are not. I, unfortunately, cannot explain it briefly. But remember that these conjunctions are usually used and easier to understand when you think of them as "apart from" and "except for" so to illustrate let's use Sara's sentence. "Everyone is here apart from you" and "Everyone is here except for you" (this has the same meaning) But if I used my dogs in a sentence "My dogs must be kept apart from each other." (or they will fight - this makes sense) and "My dogs must be kept except for each other" (obviously it does not make sense, so it's not interchangeable in every circumstance)