Google Adwords is a platform offered by Google that allows you to advertise on the internet. There are many types of advertisements that you can create using Adwords, but the two common types are Google Search Ads and Google Display Ads. Display Ads refer to ads that are banners that appear on website. Search ads appear in search results.
When using the Display Network you can target your ads in multiple ways. One way to target your ad is to select specific placements, or sites, to display your ads. Another way to do it is to use Contextual Targeting, which allows you to tell Google the types of site, identified by keywords, that you would like your ads to appear.
Google Adwords is fairly complex and you can loose a lot of money if you don’t operate it correctly. I strongly recommend learning as much as possible about Adwords before you go running campaigns through it.