Files produced by word processors use non alphanumeric characters to indicate formatting information such as the size and shape of text.
This is the same way most word processors work.
They may also be viewable using some other word processors.
In some cases, free word processors do not allow formatting that is WYSIWYG or "what you see is what you get" that most writers will be familiar with.
While the program is relatively basic, it is one of the free ones that most resembles well-known word processors such as Pages for the Mac and Microsoft Word.