SanskarPandit If you upload photos, it will take up space in your cloud storage, but the default image compression is pretty good so lots can be stored in a small cloud account.
You attach tags to entries to help you find all entries of a certain topic. I tag 'work', 'meals out', 'sunrise', 'walking' etc. You can tag people too.
Files are for attaching things like PDFs to an entry.
Diarium isn't a subscription model, so once you've bough it, you can use it 'indefinitely'.
You can export entries as .doc .txt and .html from whatever date range you want - you can even have a separate file for each date, so if you're worried about the app being discontinued, you could make regular exports to keep your journal outside of Diarium.
Hope that helps.