It’s called affiliate marketing, when you have a blog you can embed ads on your blog, that is how most people make money from blogging.
Types of ads you can put on your site to make money online:
Advertise on your blog that you are looking for advertisers.
This is one of the easiest ways to start making money from your blog, if you have loads of traffic you can get someone to contact your personally and get them to advertise on your blog.
Use embedded ads
This is mostly the one that’s used. Use something like Google adsense to make money from your blog by embedding ads that generate the same ads given by customers to fit your content. That way people will click on it easier because it has to do with what they are reading at the moment.
Write reviews
There are many places online that you can write reviews to make money online blogging. Some include linkworth and payperpost. Linkworth is easier to get into whereas text link ads and payperpost is a bit full of crap.