Those might be temporary files used by an app you installed - I don't have the directory. The name of the app may be related to the initials "BR".

If you know what app that is, then either go into that app and delete the files via the app's user interface, or go into Applications, find the app and tap it, then click the "Clear Cache" button. These options are the safest.

In any case, if you want to delete the files directly yourself, then in ES File Explorer tap and hold a file and pick "Delete" from the menu.