It is a noun that has two meanings.
The first is "this time" and it is used to describe a current timing to do something that is done several times. It is interchangeable with "今回".
The second means "next time" and it is used to describe another time when something will be done in the future.
I’ll take the JLPT this Friday. I definitely want to pass the exam this time because I have just two months left before I go and work in Japan.
- Tom: ごめん。明日、横浜に連れて行けないや。休暇を取る予定だったんだけど、仕事に行かなきゃいけなくなった(orチームメンバに頼まれて、出社しなきゃいけない)。
I'm sorry I can't take you to Yokohama tomorrow. I know it was supposed to be my day off, but my team really needs me and I couldn't say no. - Meg: えっ、そっかー。いいよ。プロジェクトが山場を迎えているだよね。また今度行こう。
Oh, okay. Don’t worry. I know you're on a sensitive phase of the project. We’ll go some other time. - Tom: (わかってくれて)ありがとう。今度、埋め合わせ(を)するよ。
I knew you would understand. I'll make it up to you, I promise.
- Ken: 今日の仕事は、これで終わりだね。飲み行く?
I think we’ve finished work for today. Do you want to grab some drinks? - Leo: また今度行かない?まだやる事が沢山あってさ。
Maybe next time, okay? I still have a lot of things to do. - Ken: いいよ。あっ、来月の頭に出張(が)入っているよね?今度(or今回)の出張は、ビザが必要だよ。もう取った?
Okay. Oh, you're supposed to go on a business trip early next month. You need to get the visa for the next trip. Have you already gotten it? - Leo: まだ。リマインド(or知らせてくれて)、ありがとう。
No. Thank you for reminding me.