In the last few years a new technology sector has emerged with the goal of creating more efficient and trackable currencies, higher quality AML/KYC, and decentralized financial ecosystems.
We call the technology "blockchain" and the digital assets on it "tokens". To date, the industry has been rife with scams as well as largely operated without regulatory permissions.
However, there are many companies coming under the regulatory umbrella and willing to work within the U.S. SEC and FINRA securities frameworks. These companies are listing securitized tokens (tokens as securities).
A basic example of the goal of blockchain would be: if your friend gives you a dollar, you have no idea where that dollar has been. A distributed ledger on the blockchain could capture and track every transaction of that dollar to it's creation date while comparing it to other "blocks" and "nodes" across the ecoystem to ensure the dollar is the original.