Blogging is another popular way to earn money online. It simple words a blog is something like a personal online diary. You can write about something you like or anything you like to write. success of the blog will depends on how much you know about the blog topic. People like to read about other peoples personal experince and recomendations so this has become popular way to earn money online without knowing much about web site design or related things.
There are few different methods of blogging or using a blog. such as free blogger platforms, Self hosted blogs etc. You can use them depending on your experince and need. You can earn money with any of these ways by using various ad networks or affiliate ads.