A suffix that is preceded by a decimal (". ") and that is appended to a computer file name. Note: Common filename extensions with their meanings are:. Wpd = a type of word-processing document. Doc = a type of word-processing document. Exe = executable code or a self-extracting archive file. . Gif = a graphical interchange format (graphics file. )txt = a text file. 2. Proprietary HTML tags that are recognized by a single Web browser or by those Web browsers developed by a single company.