A decompiler is a computer program that translates an executable file back into high-level source code. Unlike a compiler, which converts high-level code into machine code, a decompiler performs the reverse process. While disassemblers translate executables into assembly language, decompilers go a step further by reconstructing the disassembly into higher-level languages like C. However, decompilers often cannot perfectly recreate the original source code and may produce obfuscated or less readable code.