Different programs use different file formats to save information.
.DOCX
Usually used for Microsoft Word documents such as letters, assignments, and reports.
.XLSX
Used for Microsoft Excel spreadsheets containing data, calculations, tables, and charts.
.PPTX
Used for Microsoft PowerPoint presentations.
.PDF
Designed to preserve the layout of a document so it can be viewed consistently across different devices.
For example, if someone sends you a file named:
Computer_Course.pdf
you can immediately recognize that it's a PDF document.
Learning file types helps you understand what you're opening before you even open it.