What is a "Shard"? A Shard is a fraction of an NFT. We coined the term when NIFTEX launched in early 2020.
Do fractions give me display rights for the NFT? There are no conventions with regard to display rights in the general NFT space, hence there is no concrete answer to this question. No fractions have encountered such issues so far.
Where can I sell fractions? Most fractions will have their own bonding curve which can be found on the details page for that fraction (see also: CoinGecko market list). The bonding curve resembles Uniswap in functionality. Since the fractions are ERC20s, you can also just bootstrap a market on a popular AMM like Uniswap or Balancer.
How does Metamask work with fractions? Fractions are ERC20s. If you buy fractions, they are automatically sent to your wallet. If you need to manually add them, the address is in the url of the details page for the respective asset. If you're buying fractions in a fixed price sale, you need to wait for the sale to be successful to claim the tokens to your wallet.
Sale of Fractions at Fixed Price (Fixed Price Sale)
What happens if my fractions don't sell out (Fixed Price Sale)? You get the NFT back and everyone who bought gets their ETH back. You can reclaim at any time, there is no limit.
How long do I have to claim fractions that I bought in a Fixed price Sale? There is no time limit or expiry.
What is a Buyout? See this page.