Multipurpose Internet Mail Extensions (MIME) is an Internet Standard that extends the format of e-mail to support text in character sets other than US-ASCII; non-text attachments; multi-part message bodies and header information in non-ASCII character sets. Virtually all human-written Internet e-mail and a fairly large proportion of automated e-mail is transmitted via SMTP in MIME format. Internet e-mail is so closely associated with the SMTP and MIME standards that it is sometimes called SMTP/MIME e-mail.
MIME Types tell browsers how to handle specific file extensions. For example, the text/html MIME Types equates to .htm, .html, and .shtml extensions on most servers, telling your browser to interpret all files with those extensions as HTML files. You can alter or add new MIME Types specifically for your site (Note: You cannot alter the system defined MIME Types values). MIME Types are often used to handle new technologies as they appear. When WAP technology first appeared, no one had these extensions set up on their server. With MIME Types, however, you could have set it up yourself and began serving WAP pages immediately.