Module 01 · Free
How Search Actually Works
Understand the machine before the tactics: what a query is, how pages are fetched, how they are stored, and what 'relevant' is computed from.
5 lessons · 7 videos · 2h
- 01.01
What a Query Actually Is
Break a single search phrase into the intent, the implied constraints and the ambiguity a ranking system has to resolve, and explain why 'best crm' is three different questions wearing one set of words.
- 01.02
The Crawler: Frontier, Budget and Politeness
Describe how a crawler chooses what to fetch next, why crawl budget exists at all, and what Googlebot actually requests when it visits a page.
- 01.03
The Index: Your Page Is Not Stored as a Page
Explain tokenisation and the inverted index, and say what actually gets looked up when someone searches - a posting list, not your document.
- 01.04
Scoring Text: TF-IDF and BM25
Compute why one document scores higher than another for the same term, and explain what BM25's saturation and length-normalisation terms are correcting for.
- 01.05
Links as Votes: PageRank and What It Became
Explain PageRank as an eigenvector over a link graph, and say honestly which parts of that idea still operate and which were replaced.