I used to use Bloglines to read all my blog feeds, then I switched to Google Reader as bloglines was lacking in some capabilities I wanted.

Here is the Google blog and a tip on using the reader.

Official Google Reader Blog: J-walking with Reader

And you ask what is a blog feed. Well it is the blog postings sent to your reader by RSS or Really Simple Syndication. It allows you to aggregate the latest postings from many blogs into one page, read them, mark them a read or star them for later reading.