Cardano is an open source, decentralized blockchain as well as a platform for executing smart contracts. These features allow you to create, deploy and maintain dApps. But Cardano aims to provide more advanced functionality than any other previously developed protocol. It is the first blockchain platform to evolve from a research-based approach. The development team is made up of a large global collective of engineers, researchers and scientists.
Cardano justifies its existence for several reasons. It all started with first generation cryptocurrencies like Bitcoin. Two people can exchange value without using a trusted third party. The "problem" is that the exchange of value comes from a contract, for example: "I give you 1000 € in exchange for your computer" ... Bitcoin was not suitable for this and quite heavy overlays have were built on top of Bitcoin to meet this need. In 2014 Vitalik Buterin, Charles Hoskinson and others came together to offer Ethereum.
This cryptocurrency allows you to add a programming language to blockhain (Solidity). This will automatically trigger an exchange when conditions are met. These are second generation cryptocurrencies. But Cardano sees limits to Ethereum which cannot be very scalable. Scalability means that a blockchain is able to support the increasing load of its network (for example the increase in transactions per second while maintaining its performance). There are different points of view on how to try to implement scalability solutions. The result is hard and soft forks like Bitcoin and Bitcoin Cash for example.