What does Shards mean in SEO?
Shards refers to a method of storing information and which some believe may explain why new pages bounce around in the rankings for a while.
Let me just explain a shard. Imagine the entire Internet in three dimensions, each page hanging out there in space and links between them as straight lines. It really would look like a spiders web and it grows in size and changes at a phenomenal rate.
New pages appear, old ones become extinct, a webmaster over there deletes a link they had made to another website, a webmaster over here creates one.
For search engines like Google this represents a problem. Even with their immense computing power checking 'how the Internet has changed' would take a long, long time and so in essence their rankings would always be out of date.
New content that could provide a better user experience in the search results doesn't show up there while people find that clicking on some links sends them to websites or web pages that no longer exist.
So what is a search engine to do?
Let's go back to that imaginary vision of the Internet again. All the pages hanging in space with lines to each other representing links. Instead of trying to understand the whole thing its easier to understand one aspect of the whole thing. Do certain pages clump together?
Pages about spine surgery, for example, tend to link to other pages about spine surgery but rarely link to pages about SEO and vice versa. So lets put all the pages about spine surgery over there and all the pages about seo over here. Now it looks less like a spiders web because there are clear 'clumps' of pages when it comes to how they link and what topics they cover.
Now as a search engine you could consider each of those clumps individually rather than trying to do all of it. Each part that you break out, each clump, is known as a Shard
in database speak.
Now you can have multiple computers all working on updating a shard making it much faster to get an accurate picture of the Internet. If one shard becomes to large computers can analyze how it could be broken down into more shards.
So what is a shard? Just a bit of the Internet that you broke off like a piece of chocolate from a chocolate bar because its a bit tricky to eat an entire chocolate bar all at once - in other words 'bite sized chunks' in computer speed.
Google uses shards to ensure what you see in the search results is up to date, ideally almost in real time.
But in looking at the Internet this way, in shards and not as a whole, it is not always easy to understand the true authority of an individual page. What about a page in which someone blogs about how they search engine optimized their spinal surgery website?
Lets say in the shard of spinal surgery their website has a great deal of authority then their SEO page might appear to have a lot of authority to. If you compared it with websites about how to SEO pages it might be very weak but Google doesn't, it compares it with what else is in the shard.
Then when it glues all the shards back together we see pages with little authority sometimes ranking very highly and asking, "How did they do that?". Its an argument put forward by people like Roger Monti over at Search Engine Journal
But its theoretical and even if there were something in it, it would clearly be a known issue that Google engineers would want to solve so trying to make it work for your search engine optimization would be a complete waste of time in the long term.
Shards - OK, nice to know how search engines go about their business but not essential when it comes to understanding SEO for long term rankings.