Assemblers are programs that convert assembly language, a low-level programming language, into machine code, which is the binary code that a computer's processor can execute. Assembly language is closely related to the architecture of the computer, making it easier for programmers to write instructions that the hardware can understand. The process of assembling involves translating human-readable instructions into a format that the computer can process. This is essential for software development, as it allows developers to write efficient code that interacts directly with the hardware, optimizing performance for applications and systems.