There are hundreds of thousands, if not millions, of blogs on the internet. They are very easy to set up and there are many platforms that you can use but 2 dominate the market. One is Blogger.com and the other is Wordpress com. I have both types. This particular blog is on Blogger but Wordpress blogs are somewhat more sophisticated and a bit more difficulat to set up. Blogger is free including the hosting. Wordpress blogs are usually set up using a person's own domain and hosting.
You can write about anything that interests you or that you might feel that others would find interesting. You can actually make money doing this, at least they tell me that you can make money doing this. If you look in the margins and underneath the current posts, you will see ads by Google, as an example. If your visitor clicks on the ad, the owner of the blog receives money from Google. This might be an enjoyable way to supplement retirement income.
This guy offers video training on setting up a Wordpress blog. This is how I learned to do this. His site is