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.
XLSX is a file format created with Microsoft Excel, version from 2007 and younger. This file is a spreadsheet. All data distributed document and stored in the cells. Each cell has a unique address, which is denoted by the letters and Arabic numerals. XLSX file format is based on the Open XML. To reduce the size of the file is compressed ZIP.