What do you know about Nielsen? - global provider ...

Nielsen is a global measurement and data analytics company that helps businesses understand what people watch and what they buy. It collects huge amounts of data on consumer behavior and media usage, then turns that into insights clients can use to make better decisions. (Nielsen)

Here’s a cleaned-up version of your notes you can use as a short description:

Nielsen is a global provider of market research and analytics that focuses on what consumers watch and buy. By combining large-scale consumer and market measurement with advanced analytics, Nielsen helps clients see the big picture of consumer behavior across channels and devices. It works with media companies, advertising agencies, FMCG/CPG manufacturers, and retailers to measure audiences, track sales, and uncover insights that drive marketing and business performance. (Vizologi)

And mapped to your bullets:

• Global provider of market research & analysis → operates in 100+ countries, measuring media and markets worldwide. (Wikipedia)
• Based on consumer and market measurements & analytics (“watch” and “buy”) → classic positioning is “what people watch and what people buy.” (Sage Tips)
• Takes data & analytics and applies it to the big picture for client success → integrates audience measurement, retail measurement, and advanced analytics for strategic decisions. (Vizologi)
• Looks at consumer behavior from a variety of perspectives → media exposure, shopping behavior, demographics, lifestyle, etc. (Nielsen)
• Serves media companies, agencies, FMCG/CPG manufacturers, and retailers → core customer base across media and consumer packaged goods. (Vizologi)

If you tell me what you’re using this for (CV line, interview answer, presentation, etc.), I can tailor it into a perfect 1–2 sentence version for that context.