How do people on facebook do this?

[Rad]

The fact that you can share a picture gives the ability to have "viral" pictures spread throughout the internet. You've probably seen this especially for memes or "cat pictures", whatever. Social media is a great way to market/advertise graphics and is actually a platform for distributing this sort of thing.

You don't need any special tools or features to do this though, you just need some people with common interest to spread the word about your content. As long as your photos are good, they will be recognized. If you can find ways to encourage people to share your pictures, that's great. Getting subscribers and likes is important.

You would probably be surprised how important Facebook pages are for companies, websites and even photographers.

Reddit, imgur and similar websites can also spread publicity, but only if the photos are meaningful. Just trying to advertise using those sites will likely have a negative effect, but if your posts are earnest then you will benefit from them.