「、・・・」「」
'Uh, this "gōkon" thing is basically...' 'Just a regular mixer.'
Literal
''Um, that mixed-meeting [quotative-というのは] in-short...'' ''Ordinary [possessive-の] compa is [emphatic-よ]''
Defining types of social gatherings. 合コン (ごうコン) is 'group date, mixer' — typically organized with equal numbers of men and women meeting for dating prospects. コンパ ('compa') from English 'company' is any social gathering/mixer, general term. つまり ('in short, that is to say') signals a summary definition. The dialogue is someone asking for clarification and getting the plain-english version.