adverb, noun
at that time; in those days; then
Refers to a past period already mentioned or understood from context. Often used in narrative or reminiscing.
See also: その頃
この頃はまだ子供だったので、何もわからなかった。
At that time I was still a child, so I didn't understand anything.
この頃、彼は毎日遅くまで働いていた。
In those days, he worked late every day.
その頃 refers to a time closer to the listener or a previously mentioned time, while この頃 refers to a time the speaker is recalling or a period just mentioned by the speaker.
Compound of この (this) and 頃 (time, period). The kanji 頃 is used for approximate time.