According to what I knew and I have found on the web, in general the word casual is the opposite of everyday. But in the special case when it refers to clothing, it has a similar meaning to "everyday clothing". And it definitely does not mean "special" or "formal".
This seems illogical to me. Could you please clarify? Is that really the case?
This is especially confusing to me, because in my native language (Hungarian), the literal translation of casual is the same word that is used to refer to formal clothing for special events. This seems to make more sense.