Google is a search engine provider, but it makes it money through selling ads. Naturally they're very tapped in to what people look for online. The primary tool is their Google Analytics software (we have a whole article on how to disable Google Analytics, if you don't like the idea of being spied on). They record the number of searches and gather basic information on who's looking at what. Nothing too Orwellian, but a few details on what regions and countries search for.
If you'd like to tap into the lightest version of this, then just fire up Google Trends (trends.google.com). Google Trends is incredibly simple to use. You just type in a keyword and it will show you a chart detailing the rise and fall of interest in it over the course of the last few years. It also features a list of hot topics with long charts showing the breakdown of traffic based on countries.
The program also lets you run comparisons between interesting keywords. If you search for more than two a time and separate them with a comma, then it will show side-by-side comparisons. I did a search comparing the terms "parrot" and "parakeet". It seems that parrots get much more attention and a lot of searches from people in South Africa.
You can also check out individual website traffic through the same methods, if you're interested in how many people an individual website gets each month.
The best part is that it's just as easy to use as Google, so if you were able to find this article you're probably able to use Google Trends. It's a little lacking for professional information, but it's fairly fun and a good way to find out about the latest trends online.
Image Credit: Screencap by Author - Picture of Google Trends Comparison - Trends.Google.com