The anchor volume of the MOS Pathway series, a Vietnamese-language certification-prep program for self-studying learners aged 14 to 19 preparing for the Microsoft Office Specialist (MOS) Associate exams. This volume teaches no application procedures; across seven prose-led chapters it establishes the shared groundwork the later volumes depend on: what the MOS credential actually is, where it sits among Vietnamese computing certifications (Chuẩn CNTT, IC3, IIG Vietnam) with an honest account of its real value, how a live in-app MOS exam runs and is scored (1000-point scale, pass at 700), the common Office interface (ribbon, Backstage, Quick Access Toolbar, file formats), how to learn software skills durably through worked examples and retrieval practice, Office in the AI era and the verification mindset, and how to build a workable study plan. It is grounded in the program's Layer-J research and is read first before the application volumes.