Indexing represents a formal mechanism for establishing a bijective mapping between linear sequence positions and data elements within a contiguous block of memory, whereas negative indexing denotes an arithmetic offset operation that traverses the sequence in the reverse direction relative to a defined terminus. This concept relies on the theoretical principle of zero-based ordinality and the algebraic rule $i_{negative} = i_{positive} - N$, where $N$ is the total length of the sequence. As a foundational access protocol in computer science, it defines the syntax and semantics for direct random access to elements within ordered data structures without requiring explicit traversal of preceding nodes.
Prerequisite chain context: requires Square Bracket Notation in Python.