Polkadot is a blockchain technology but makes some innovations that sets it apart from other popular chains.
Ethereum is a smart contract blockchain that allows for general computation to be deployed on-chain and operated across the p2p network. Ethereum 1.x refers to the current Ethereum release and the immediately planned future upgrades.
The difference between Ethereum 1.x and Polkadot is quite large. Ethereum is a single chain that allows developers to extend its functionality through the deployment of blobs of code onto the chain (called smart contracts). Polkadot, as described in the whitepaper, is a fully extensible and scalable blockchain network that provides security and interoperability through shared state.
In practical terms, this means that the layer of abstraction between these two projects is remarkably different for developers. In Ethereum, developers write smart contracts that all execute on a single virtual machine. In Polkadot, however, developers write their logic into individual blockchains, where the interface is part of the state transition function of the blockchain itself. Polkadot will also support smart contract blockchains for Wasm and EVM to provide compatibility with existing contracts, but will not have smart contract functionality on its core chain, the Relay Chain.
As such, Polkadot is a possible augmentation and scaling method for Ethereum 1.x, rather than competition.