When you acquire a name for a project you will probably never start anyway and a few months later when looking at your inventory you discover you already owned the plural or singular version as well.
When you meet friends and family for easter, christmas and birthdays and suggest domain names you have when they mention keywords during light conversation.
domains are characters/number combinations followed mainly by a .com or .de that translate into an IP address in order to show a webpage / send emails / or simply store files