Introduction to reverse engineering (what is it ?)

To reverse-engineer (RE) is an action to analyze the working details of something (a computer system, a software, a dedicated device or a file format),

To (usually) build/reconstruct a new system (a computer system, a software, a specific file format...) doing the same thing/operation  without using existing part of the reserver-engineered system,

Reverse-engineering is quite vast (from software to genetics/biology),