Open a terminal and execute this command:

mv -v ~/Downloads/{*,.[!.]*} ~/Videos/

It will move all the files and folders from Downloads folder to Videos folder (including "hidden" files).

To move all files, but not folders:

If you are interested in moving all files (but not folders) from Downloads folder to Videos folder, use this command

find ~/Downloads/ -type f -print0 | xargs -0 mv -t ~/Videos

To move only files from the Download folders, but not from sub-folders:

If you want to move all files from the Downloads folder, but not any files within folders in the Download folder, use this command:

find ~/Downloads/ -maxdepth 1 -type f -print0 | xargs -0 mv -t ~/Videos

here, -maxdepth option specifies how deep find should try, 1 means, only the directory specified in the find command. You can try using 2, 3 also to test.

See the Ubuntu find manpage for a detailed explanation

TL;DR

This forces the destination to be a directory that already exists or the command to fail without effect and is used as a fail-safe.

The meaning of .

Every directory in typical Unix/Unix-like filesystems include two special directories: one referencing the directory where it is: . and one referencing the parent directory of where it is: .. (allowing to move back in the hierarchy of directories). They are relative to where they are found. So the directory . inside a directory named backups references backups. To tell it otherwise, when there's a directory named backups, backups/. is equivalent to backups.

Different behaviors with the source or destination being a file or directory

• If the directory exists, the two commands will have the same effect: when the target is a directory mv will move source(s) to that directory. That's the expected outcome.

• If the target backups is a file instead of the directory:

  • 1st case will fail with the error Not a directory
  • 2nd case will rename Caiti.bak and overwrite backups

• If the target doesn't exist:

  • 1st case will fail with No such file or directory
  • second command will rename the file Caiti.bak into the file backups, leading to the previous case and possible loss of data the next time it happens.

That's good practice to append /. to a directory target supposed to be existing and abort a script at an error from this.

All these cases would work the same when only appending / if the source is a file rather than a directory.

If we can't assume this, this example where the source is a directory:

mv somedirectory targetnothere/

would not fail (and somedirectory will be renamed instead of being put into targetnothere or abort). The extra . will make this case fail too:

$ mv somedirectory targetnothere/.
mv: cannot move 'somedirectory' to 'targetnothere/.': No such file or directory

mv command can move directories also.

find . -maxdepth 1 -exec mv {} .. \;

this will move hidden files as well.

You will get the message:

mv: cannot move `.' to `../.': Device or resource busy

when it tries to move . (current directory) but that won't cause any harm.

mv -f source target

From the man page:

-f, --force
          do not prompt before overwriting

Remove the target database directory and move the test_db directory itself. (This will implicitly move its contents, too.)

sudo rmdir /var/lib/mysql/data/test_db
sudo mv /var/lib/mysql/test_db /var/lib/mysql/data

Generally you don't need to provide a trailing slash on directory names.

Reading your comments, if you find that you're still getting a "no such file or directory" error, it may be that your source directory, test_db has already been moved into the target test_db directory (giving you /var/lib/mysql/data/test_db/test_db/...). If this is the case then the rmdir above will also fail with a "no such file or directory" error. Fix it with this command, and then re-run the two at the top of this answer:

sudo mv /var/lib/mysql/data/test_db/test_db /var/lib/mysql

The mv command doesn't have an -R flag, it moves folders recursively:

sudo mv fromPath/ toPath/

Edit

If you want a file not to be replaced, use the -i for being prompted in case a file with the same name exists.