The vault lives only inside the app. Uninstalling it or moving to a new phone loses it – unless you have a backup. Settings → Backup → Save backup stores the vault file wherever you choose (cloud, NAS, USB stick). It is encrypted with the master password that is currently valid, and it is read back after saving.
On an empty device you get your data back with Restore backup during setup. You need the master password that was valid when the backup was made.
Under Settings → Export you take your entries to another program. An export is not a backup: the trash does not go along, and the way back into EasyKeys is the backup.
The export is a spreadsheet (CSV): one column per field, plus the tags – readable by almost every password manager and spreadsheet program. This file is not encrypted – delete it once you have transferred it.
Every entry is in it with its current content. A spreadsheet cannot carry two things, and the app tells you how many before you save: