Basic of web feed

While visiting websites,You have always seen the following logo .Plus there are text like that "Subscribe to our FEED" or only Subscribe with email.You might be thinking what is it?

Feeds like publishing of updates,newer entry of a website or blog in a more reachable way.This might be a short feed with title,writer,published date,and a snippet of the post or it might be full.

In more simple words,if you subscribe a website feed with your mail then whenever there is an update or new entry there will be a mail with the feed.