What is meant by MIME?

MIME is Multipurpose Internet Mail Extensions is an Internet standard for the format of e-mail. However browsers also uses MIME standard to transmit files. MIME has a header which is added to a beginning of the data. When browser sees such header it shows the data as it would be a file
for example image
Some examples of MIME types:
audio/x-ms-wmp
image/png
aplication/x-shockwave-flash