Majestic describes themselves as “The planet’s largest Link Index database.” What they know is a lot more than I know, for sure. What they can tell you for only one of their services is how many links there are to your site and how many of them are “good links.” Good links come from sites with real content. Bad link come from link mills that only link to a lot of sites to drive traffic to their own site — where they sell various, probably worthless services or stuff.
Improve Your SEO
The reason you want good links is because they help you in search engines — Bing, Google, Yahoo, etc. There are many general search engines and some specialized ones.
Majestic also provides pie charts and data on the kind of links — text, images, etc. — and which pages are linked most often. This can be important information. Some of the pages that are linked most often are ones I had forgotten I had posted. I had to go look them up to see what was most important to my readers!