Is watching my daily calorie intake enough to lose weight?

I have downloaded an app on my cellphone where I can keep track of what I've had all day. I put both my foods, drinks and exercises in there (although I only drink water). According to this app I should take 1800 calories a day or less to lose like 0.5kg a week. I know this app isn't 100% accurate so I aim like 200 calories below my target of 1800, some days I have a bit more and some days a bit less.

Anyway, my question is (and maybe it's a very dumb question but I honestly don't know), do calories have everything to do with weight loss? Like if I keep getting that +/- 1800 calories will that be enough? No matter what I eat, for example pizza of 500 calories or 100 carrots of 500 calories?
Is watching my daily calorie intake enough to lose weight?
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