"What is going on?"
Translation:Cad atá ar siúl?
Please correct me if I'm wrong here.
From my understanding, "Cad é" is when you are asking questions using the copula built into "cad", e.g. "what is it?". "Cad atá..." is for situations where you are not using the copula for your question and the copula is implied, e.g. "Cad atá ar siúl", which can be thought of as implying the "é", i.e. "Cad [é] atá ar siúl" meaning "What [is it] is going on", or more naturally "what [is it] that is going on".
There are to different type of questions in English and Irish. Questions about actions involve a verb - "do you eat cheese?" - an itheann tú cáis?, "Are you ready?" - An bhfuil tú réidh?, "Does this bus go to Cork?" - An dtéann an bus seo go Corcaigh?.
In English, these question either use "do" or they reverse the subject and verb ("I am" -> "Am I?"). In Irish the involve the interrogative particle an, or the interrogative form of the copula (which is also an).
Then there are "W" question - "who", "what", "why", "when", "where" and "how". In Irish, these are C questions - cé, cad, cên fáth, cathain, cá and conas. There isn't always a one to one correspondence, and different forms of questions may be preferred in different dialects, but, to answer your question, no, most questions do not involve bhfuil.
Dialect; cad is more popular in Munster, and céard is more popular in Connacht.
I thought "atá" had something to do with "you". What does it mean? And what does "siúl" mean?
Siul = walk atá = and (but it seems to be flexibly placed as a spacer in sentences needing lenitiion?)