expression, na-adjective, noun which may take the genitive case particle 'no', noun
perfectly normal; absolutely commonplace; taken for granted
Emphasizes that something is so ordinary or expected that it is not even noticed. Often used to describe things that are considered natural or obvious in a given context.
彼にとっては、毎朝ジョギングするのはごく当たり前のことだ。
For him, jogging every morning is a perfectly normal thing.
この地域では、冬に雪が降るのはごく当たり前だ。
In this region, snow in winter is absolutely commonplace.
彼女の親切はごく当たり前で、誰も特別に感謝したりしない。
Her kindness is taken for granted, and no one thanks her especially.
Combination of the adverb ごく (極, 'extremely') and the adjectival noun 当たり前 ('natural', 'obvious'). The phrase is a straightforward emphatic form.