A token is a unit of value that represents multiple facets, such as monetary value, voting influence et al, in a blockchain network. Blockchains do not necessarily need a token to function - IBM’s Fabric and R3’s Corda are examples of two blockchains that eschew tokens.
Although blockchain networks can function without the need for a token, these networks lose much of the benefits that come with the use of a token - user incentivization, for example. However, it is true that some enterprise level permissioned networks would gain benefit from simply deploying a distributed ledger without a token.
Several kinds of tokens exist, though they have informally been categorized as being either utility tokens or security tokens. Utility tokens are those that let a user further avail a platform’s services or products - Basic Attention Token (BAT) is a good example of a utility token. Security tokens are more like traditional investments - these tokens are those for which the user expects some kind of return after a period of time.
Another important element of a digital token is the fact that it can be used as a virtual representation of a physical or traditional asset, such as gold, real estate and commodities. This has several benefits for the investor.
By tokenizing a piece of land or gold into fractional, digital units, it allows investors to make a fractional investment in the asset, affordably and conveniently, as they do not have to pay a large sum or worry about maintenance and possession. This is perhaps the most discussed property of tokens.