Digital Marketing Ultimate Course Bundle - 13 Courses in 1

Return on ad spend is the revenue a campaign produced divided by what it cost, expressed as a ratio or a percentage: five pounds of sales for every pound of advertising is a ROAS of 5, or 500 per cent, and the number only becomes a decision once it is compared with the margin on those sales.

Digital marketing is the trade name for every commercial activity that reaches a buyer through a screen, gathered under one heading because the work is bought, delivered and counted through the same few platforms rather than because the activities resemble one another.

SEO is the work of being retrievable and worth retrieving: legible to the systems that crawl, index and select sources, and useful enough at the moment of the query that somebody still opens the page instead of accepting the answer printed above it.

SQL is the declarative language for asking questions of relational databases: you state which rows and columns you want and how tables relate, and the database engine works out how to retrieve them.

ETL is the pattern for moving data from the systems that produce it into the one place it is analysed: extract the records from each source, transform them into a common, cleaned shape, and load them into a warehouse; ELT keeps the same three steps and runs the transformation inside the warehouse after loading.

A data warehouse is a database built for analysis rather than for running the business: it holds copies of records from many operational systems, integrated under one set of definitions, kept as history rather than overwritten, and arranged so that questions across years and departments run fast.