You can use TextEdit to open, edit, and save files in a variety of formats:
Plain Text (.txt)
Rich Text Format (.rtf)
Rich Text Format Directory (.rtfd)
HTML (.html)
Web Archive (.webarchive)
Open Document (.odt)
Microsoft Word 2007 (.docx)
Microsoft Word 97 (.doc)
Microsoft Word 2003 XML (.xml)
Files saved in formats other than plain text can include graphics, paragraph and font formatting, tables, and lists.
Most word processors can open RTF files. Microsoft Word can open files in Word format. TextEdit supports a number of Word features, including tables, but some other features may not be supported.