Can someone explain what does it mean?
In simplistic terms, traditional APIs which have a single point of failure. If the API goes down you can no longer communicate to get the data you need. A decentralized API (dAPI) allows clients to connect to different instances depending on resource availability. For example, if a masternode goes offline, taking its decentralized API instance with it, then clients will be able to seamlessly connect to and retrieve their application data via another instance because multiple nodes are running, each with their own API.
Just like a decentralized network, if one client goes offline the integrity of the network is still there. Thus, dAPIs are automatically scalable and provide infinite elasticity, limited only by the total number of nodes. Due to the decentralized execution, they scale horizontally with low latency and automatically adapt to user demand and data load.
@Harry cut is correct. API keys are used to interact with services from third-party programs without giving access to the account.
For example: let’s say you want to use any other bot/trading service with the exchange, such as 3Commas. Right now in every non-custodial exchange (doesn’t matter how decentralized its business or technology is) you need to provide access to your private keys to the service or the exchange must take custody of your funds. Since a few months we have been working on a technology to this problem so that the user experience of using bots and those trading services can be as close to the “standard” as possible, so people will be able to use it without giving full access to the private keys.