the matter in question; that issue; the thing we're talking about
A fixed phrase used to refer to a previously mentioned or contextually understood matter, often in business or formal conversation. Functions as a noun.
Regarding that matter we discussed, how is the progress?
Has that issue been resolved yet?
A set phrase combining 例の (that well-known) and 件 (matter, case). The exact historical derivation is uncertain, but it is a conventional collocation.