Incoming emails arrive in sub-folder All mails, instead of arriving in Inbox - how do I correct this?

Hello! Would much appreciate info on how to fix a problem that appeared today. All incoming emails wind up in sub-folder All mails, instead of arriving in Inbox as usual. Also, two dozen emails that came in today got transferred to the All mails folder. These emails are not duplicated in any other folder. I may have pressed a wrong key on my keyboard without wanting to. Updates: Right-clicked Inbox and pressed Repair button. All mails vanished for 1-2 seconds, then reappeared, ordered as before. Incoming emails, including a test mail I sent from my other email address to my TB, now arrive in Inbox and sub-folders All mails and Important. When erasing a mail in Inbox, I erase it from All mails and Important simultaneously. Now my TB seems to function as before. Included the above updates in case they are informative. Many thanks in advance for all help!