Google Trends is a Google website that shows search interest: the relative share of Google searches that concern a term or topic. It draws on a largely unfiltered sample of real search requests made to Google, which Google anonymizes, groups by topic and aggregates, so interest can be shown for the whole world or down to city level.
On the Explore page a user enters terms and compares them by time range and location; the Trending now page shows searches that are rising. Each data point is divided by the total searches of its place and time and then scaled from 0 to 100, so the numbers show relative popularity, not search volume. Trends drops searches made by very few people (shown as 0), repeated searches by one person in a short time and queries with special characters, and it adds small random noise to protect privacy. Google notes that Trends is not a scientific poll.
Google offers it as a website; the pages read state no price.