Really great question! Tl;dr decompiling bytecode just means parsing it to a more human readable format. Bytecode is basically machine-readable source code - it's not meant to necessarily be impossible to read or reverse engineer - ultimately, the computers executing the smart contract code need to be able to understand what it's telling them to do! ​ So bytecode describes all the functions written on a smart contract in a way that machines can read them, and that humans can also technically decode - it's just very, very difficult for us to read! So what decompilers do is basically they have a computer parse all the code and then translate it back into a more human readable format. ​ However, this isn't exactly ideal or anything close to having the real source code - decompiled bytecode loses all the comments written in the original source code to describe all the functions, and doesn't exactly write the code the way it was originally written - it just converts it to a standard decompiled format. ​ Smart contracts on Ethereum actually retain a lot more of their function and variable naming than other decompilers would be able to decipher in other situations, so it's actually still pretty surprisingly readable - you can see an example of a decompiled bytecode contract using the Panoramix decompiler that Etherscan relies compared with its original source code here: https://oko.palkeo.com/0x06012c8cf97BEaD5deAe237070F9587f8E7A266d/code/ ​ And you can see all the function names and most of the variable names are preserved, with a few exceptions. ​ The code is also surprisingly readable, though not nearly as readable as the original source code, which you can clearly see in the side by side comparison! ​ Hope that helps! You can read more about how decompilers work from the great Wikipedia article on them: https://en.wikipedia.org/wiki/Decompiler