Many large websites today are full of ads and AI algorithims stealing your data and exploiting it for profit. For example, on YouTube, you will usually have to watch two or three ads before getting a whole ten minutes before another ad. You may have noticed that a lot of these ads seem oddly personal, and that's thanks to all the data they are collecting from you. This data is usually non-sensitive, but can include things like location and credit card info (if you are paying for a subscription). With your own personal website, all of this datamining and endless bombardment of ads can be easily... adverted. ;)
Most businesses now adays have websites, which usually hold information about the business. If you own a business and don't have a website, it may be harder for you to get recognized on the internet. Having a website for a business will allow your store to show up on search engines like Google or Bing. Having a website for your shop will also allow you to spread word of it online more easily, as just sharing a link is easy.
What about back when people did make their own websites? Back in a time when dinosaurs walked the Earth... 2000-2009! Even though some of the large networks of today (or the past) had begun to form, like MySpace, many people who wanted to share some things they made would create their own website, usually just to share with friends. Hosting services like GeoCities provided a free service to users in which they could create a personalized webpage. These sites were primitive, didn't look so good, (like mine,) and were not professional in any way. But they had what modern sites don't: charm.
Relating to business, branding. Even if you don't own a business, having a website that is business-related can be helpful. It could make you look more professional, and once again, easier to find from google searches. You could list your expierences and what you do, and have it seem more human from the handcrafted look. Less related to branding, you could use it to make a blog, or other many social-related activities, which you could keep more private.
🐖Ooh la la... look at that! You really can customize stuff. Modern social media sites today tend to only have three options for customizing your account: a banner, a profile picture, and your username🐖With your own website, you can do random stuff like this. Websites can be much more personal and feel more alive than the same old three options you will get now adays on most websites.🐖
Just becuase you own the site does not mean you can just throw information around like willy-nilly. Even if you are not popular and no one is searching for you, putting up information like your phone number or real name can be dangerous. If you built a fourm board for your site or something that requires account creation, keeping it safe from hackers is key. Leaving data unencrypted in a not-so-secret page without any passwords required is a horrible idea.
Short answer is programming. Websites are made from three different programming languages, being HTML, standing for HyperText Markup Language, CSS, standing for Cascading Style Sheets, and JavaScript, which doesn't stand for anything. HTML functions through the use of angled brackets, or these things: <>. Different things are defined using identifiers inside of the angled brackets, like h1 through h6 for headers, p for paragraphs, ul or ol for lists, and so on. each tag ends with a /, and then the starting tag. An example script would look like this. CSS defines the style, or the looks, of the website. This is how the boxes that make up this website work. CSS controls font family, color, size, background images, margins, background colors, sizing, spacing, and much more. JavaScript is for math functions and is generally a more normal programming language. It is sometimes describe as the "wizard" behind webpages. Most webpages would cost money and are hard to use, but some are free and quite easy to learn.