Salaries for bloggers vary widely. This report from Glassdoor shows ranges from $19K to $79K a year for the title "blogger," while other sources say the 14% of bloggers who earn a salary make, on average, $24K a year (or $33K for corporate bloggers). Likewise, freelance bloggers can make anything from under $10 a post to $100 or more for a relatively short post.
Once you setup your account on AdSense you will be given a code to add to your blog. This code will automatically display advertisements on your blog from companies who are part of Google’s advertising network. You may see ads from small companies related to your topic, or you may see ads from large companies that are completely unrelated to your topic.