Adwords is an advertising program
Adwords is a piece of Google software that allows you to advertise on Google's advertising network. If you start an AdWords campaign, you'll make the ad, but you'll also indicate which keywords the ad should appear on. The position (at the top of the first page, or somewhere afterwards) depends on how much you are available to pay. Good (top) positions cost more than lower positions. It is not, however, that only the money amount affects the position, also the quality of the link counts with the algorithm that determines who gets what position. As an advertiser you only pay for the clicks, so if someone doesn't click on your ad you don't have to pay. If your ads are placed on google.nl on the search results, then a lot of people can see your ad and click through. It can therefore be useful to set a certain limit (amount X per day) or to see if your website and back office can accommodate the flow of visitors. You can also place the AdWords campaign on Google's ad network, and you'll be taken to other websites (website using AdSense). You can place text, image and video ads, see detailed statistics, determine budgets, etc. AdWords is a system that can be used with 10 euros, but also with 100,000 euro and is therefore useful for everyone. How you decide about Adwords is right for you business, Milosz Krasinski writes an interesting article about it.
Https://www.youtube.com/watch?v=CzTT2TKTWIM
Here's an infographic to make it clear how the bidding system works 