EVM
Ethereum's virtual machine, and the de facto standard that many other chains copy so the same contracts can run on them.
The EVM is a stack machine with 256-bit words, and contracts written in Solidity or Vyper are compiled to its bytecode, with each opcode carrying a gas cost that reflects the work and storage it imposes. Its importance comes less from its technical design than from its network effects: wallets, block explorers, libraries, auditing tools and developer knowledge all target it, so a new chain that runs EVM bytecode inherits an entire ecosystem. Compatibility is a spectrum, and chains vary in gas schedules, available precompiles, opcode behavior, and block timing, so identical bytecode does not always behave identically. Readers meet the term whenever a chain is described as EVM-compatible or a rollup as a zkEVM.
Na prática
Deploying the same contract bytecode to several EVM chains is routine, but differences in gas costs or block timing can change how it behaves in practice.
O equívoco comum
EVM compatible does not mean identical; differing gas schedules, precompiles or timing can make the same contract behave differently on another chain.