An adverb meaning 'the other day / recently / previously.' Common in everyday speech.
この前、友達と食事に行った。
The other day I went out to eat with a friend.
この前の週末は雨だった。
Last weekend (the other day) it rained.
この前見た映画は面白かった。
The movie I saw recently was interesting.
Noun/adverb meaning 'last time' (the previous occasion). Used to refer to the prior instance of something.
この前のテストは難しかったね。
The last test was difficult, wasn't it?
この前の会議で決まったことを確認しよう。
Let's check what was decided at the last meeting.
この前はお世話になりました。
Thank you for your help the other day.
Refers to the previous one in a sequence (e.g., 'last [Sunday/summer]', 'the preceding [holder of a post]'). Means 'previous' in the sense of preceding in sequence.
この前の会長はとても人気があった。
The previous chairman was very popular.
この前の夏は暑かった。
Last summer was hot.
この前の約束を忘れないでください。
Please don't forget the previous promise.