Non-Fungible Tokens (NFTs)
Non-fungible is a term used to describe something unique, an item that is unable to be replaced by another equivalent/identical item, as, although they may be "identical" in form or style, there is something that differentiates them from each other, E.g. a unique ID (in the world of NFTs) with its own history of ownership, sale, etc. Conversely, a fungible item (not unique, exchangeable with any other identical item) would be something like a dollar bill; all dollar bills are equivalent to $1, and any dollar bill could be traded for any other, and retain the same value and meaning. A token is a digital representation of an asset on the blockchain. So we can say an NFT is a digital representation of an asset on a blockchain that is unique and cannot be replaced by other similar/"identical" digital representations.
All NFTs are created via a minting process that records all the asset info on the blockchain including a unique ID and assignment of ownership to the minter. The minting can be done in different ways, like opening card packs (such as in Splinterlands and GLG), airdrops of cards/items, and promotions.
Various projects such as Cryptokitties or Cryptopunkz were built around an NFT ecosystem, in order to promote ownership and the trading of digital assets on their platforms.
NFTs in Splinterlands
In Splinterlands, NFTs can be found mainly in the form of cards, specifically units and summoners; although multiple cards can be printed for the same units or archon, with similar stats and properties, all of them have a unique card ID which will differentiate them, and provide a history of ownership and sale of each specific card. The card ID in the image below can be found by clicking a card in your collection or the markets (sale or rental), with each individual version of that card showing its own unique ID. You might own 4 copies of the card below, the Ruler of the Seas, each of which will have its own ID.
Splinterlands also now has Land, which, depending on whether or not it has been claimed, may or may not be an NFT. Initially, all land will begin as a 'claim', which is NOT an NFT; we describe it as a fungible token, as there is nothing unique about it yet, and it can be traded for any other equivalent claim. After claiming, the land will have its own ID, making it an NFT. A player will not know where it is located, or the type of land and various other factors, though these are not what makes an NFT. After surveying land, those things will be determined, making it perhaps more unique from a player's perspective. However, it will still have been an NFT before that process began.