XLSBMicrosoft Excel Binary Spreadsheet File
XLSB file format specifies the Excel Binary File Format, which is a collection of records and structures that specify Excel workbook content. The content can include unstructured or semi-structured tables of numbers, text, or both numbers and text, formulas, external data connections, charts and images. Unlike XLSX (which is based on Open XML file format), the XLSB represents binary Excel workbook file.
XPSOpen XML Paper Specification
An XPS file represents page layout files that are based on XML Paper Specifications created by Microsoft. This format was developed by Microsoft as replacement of EMF file format and is similar to PDF file format, but uses XML in layout, appearance, and printing information of a document. It is, in fact, more justified to say that XPS is an attempt on PDF, but couldn't get enough popularity as owned by PDF for a number of reasons.