There are so much blog in this world. Millions I guess.
There are scripts that you can find online that can be added to your blog and it counts how many people are currently viewing your blog and how many people have been on your blog since a certain date. I have tumblr, and there are many blogs that have this.
a lot
No, but at Wordpress you can tell how many people read your blog and where they're from.
Since blog is a pretty new word, there is none in Spanish (yet). You can use blog and people would understand, however.
It is for both comment and content sharing. Generally people use blog for promoting their business or interest.
Anyone can write the blog because blog is one type of information based on the particular topic, which will help people in many terms but if you write blog make sure that blog should be informative and helpful for people.
A blog title is the blog's name e.g. "No stupid answers". A blog address is the web address (URL) that people need to use in order to get to the blog via web browser e.g. http://nostupidanswers.com
There are lots because most people in US have internet connection.
There are many free blog platforms - Blogger, Wordpress, Typepad, Tumblr. You can start an account in a few minutes at any of those sites. Blogs are used for writing, whether about personal life or a particular topic.
People blog for fun keeping in contact sharing photos and events.
tags are keywords by which you can describe the content in the article / blog post you write. These can be keywords which people use to search, mis spellings, alternate spellings etc.,
You do not have to do anything. Usually it is enough to register your blog and you will get an address in a form of e.g. blablabla.blogspot.com You give this address to your readers and they can use it to access it.