A digital asset is something that has value and can be owned but has no physical presence.
From The Digital Beyond
A digital asset is content that is stored in digital form or an online account, owned by an individual. The associated digital data are classified as intangible, personal property, as long as they stay digital, otherwise they quickly become tangible personal property.
A digital asset, in essence, is anything that exists in a binary format and comes with the right to use. Data that do not possess that right are not considered assets. Digital assets comes in many forms and may be stored on many types of digital appliances which are, or will be in existence once technology progresses to accommodate for the conception of new modalities which would be able to carry digital assets; notwithstanding the proprietorship of the physical device onto which the digital asset is located.
A non-fungible token (NFT) is a special type of cryptographic token which represents something unique; non-fungible tokens are thus not interchangeable. This is in contrast to cryptocurrencies like Bitcoin, and many network or utility tokens that are fungible in nature. NFTs are used to create verifiable digital scarcity, for example in several specific applications that require unique digital items like crypto-collectibles and crypto-gaming.
From BTC Manager
A non-fungible tokens (NFT) are blockchain tokens that are designed to be wholly and distinguishable from each other. Using unique metadata, avatars, individual token IDs, and custody chains, NFTs are created to ensure that no two NFT tokens are identical. This is because they exist to store information rather than value, unlike their fungible counterparts.