TXT is a file format that contains the text, organized in rows. Text files opposed binaries that contain data that is not intended for interpretation as a text (encoded sound or image). The text file can contain both formatted and unformatted text. Since the very simple text files, they are frequently used for storing data.
CUR is a file - the image of the cursor, sometimes animated, which is used for the mouse pointer in Windows. This may be an arrow (for general use), rotating hourglass (wait), or the symbol I (editing). Users can change or edit the standard cursors. To view and edit files .CUR suitable programs such as Inkscape, Corel VideoStudio.