Blogging is an awful term I find, and it really doesn’t explain very well what it actually is and how useful it can be to oneself. Let me see if I can explain this.
The word blog is short for weblog and has started as an online journal many years ago. All you could do was write up a diary entries and share them with the world. Many people still do it just for that, but of course you can share any writing / picture / video combination nowadays.
What made blogging popular was the addition of a comment field at the bottom, so other people could interact with your particular entry. Say one day you’ve visited The Alamo in Texas and write about it, then the next day someone leaves a comment and adds some information to your post in the form of a comment. Now it’s a mini-discussion which is even more interesting for other people to read. This interaction has replaced many traditional forums which were often all discussion without an article. You as the author have control over those comments so you can delete them, amend them or answer them (this is called moderation).
Blogging is a great way to keep in touch with your audience, but the tools to write blogs are now so powerful that they have largely replaced static websites. Even if you’re not blogging you can use the same tools (like WordPress) to generate a page that doesn’t change much – but when you want to make a change, it’s very easy to reword a passage on a page or add a picture for example.
Blogging Platforms are also known as Content Management Systems, and your content would be those blog entries. But you’re in no way restricted to using it as a personal diary of course. It’s useful for anything that you add to – like writing a book from start to finish. You can always amend what you write later, but it may give you valuable insight into a following audience. They may for example comment that they don’t follow the storyline, which is great information for any author to have. Or they tell you they can’t wait to read your next installment.
If you’re not interested in audience participation then you can switch off the comments feature altogether, or only open it on some of your posts.
Think of blog entires are your “content” – which can and should be organised. For example, a post can have several tags. If we stick to the above example of you visiting The Alamo, tags could be “alamo, texas, us, travelling, monument” and many more. If you continue your journey around the world and write about the Grand Canyon next, you might tag this next post with “colorado, us, nature”. So far so good.
Tags come in handy if you later find that you’ve written hundreds of posts, but now you (or a visitor) want to look only at posts regarding the US. Hey presto – both your Alamo and Grand Canyon posts will come up because you’ve tagged them both with “us”. Therefore finding things in your content written over a period of time becomes very easy.
Going back to your book example, if you write about a certain character, you can then find every scene you tagged with your character and maybe edit the final version of the book. That’s useful if you don’t write in he order of the final book.
Another way to organise your content is into Categories. These work slightly different to tags because categories can also have sub categories. Each post can have both tags as well as categories. The difference will become clear again when you search for particular content.
Imagine you write about cars as well as recipes, then you don’t want any car entries intermingled with your recipes. You would have a link on your blog to 
display all car entries, and another one to display all recipe entries. So far so good.
Now imagine that you’d like to bring some more order to the recipes you write about: you could have sub-categories like Chinese, Indian and French recipes. Still those links on the front page display them all, but you could have another link that only goes to French Recipes, and nothing else would be displayed. Same with cars – you could have Ford, Vauxhall and Citroen. Again finding content you add over time will become easier for yourself and your readers to find.