1. "Jump" is for jumping ahead/backwards a specific amount of bytes. Each instruction consumes a variable amount of bytes based on the amount of arguments it may have. The scripting execution environment just reads the script file, and based on where the current command is, it jumps somewhere else to continue executing next.
https://en.wikipedia.org/wiki/JMP_(x86_instruction)
2. Scripts are self-contained, so there can be multiple scripts if the file header is updated to have the relevant count & offsets to tell the game where to find script # 7, for example.
3. Not all script commands are well understood/documented (at least at the time a post may have been written/updated). If no script commands had function names, only their command # (e.g. "6"), the only way to infer what they do is to observe how the game carries out the script code and how the if-else logic results in an observable effect in-game. Logic06 is basically "this command does something with boolean/comparison logic, and is script command 06, therefore we'll call it Logic06 instead of Command06".