As of my last update in September 2021, Google AdWords has been rebranded as Google Ads. However, the core concept and functionality remain the same. Google Ads is an online advertising platform developed by Google that allows advertisers to display their ads on Google's search engine results pages, YouTube, and various other Google partner websites.


When it comes to YouTube, Google Ads enables advertisers to promote their videos to reach a wider audience. There are several types of YouTube ads that can be created using Google Ads:


1. **Skippable In-stream Ads**: These ads are shown before, during, or after the main video and can be skipped after the first 5 seconds. Advertisers are only charged if viewers watch at least 30 seconds of the ad (or the entire ad if it's shorter than 30 seconds) or engage with the ad, such as by clicking on a call-to-action overlay.


2. **Non-skippable In-stream Ads**: These are ads that viewers must watch in their entirety before they can continue watching the main video. Non-skippable ads are limited to 15-20 seconds in length, depending on the location.


3. **Video Discovery Ads**: These ads appear in places where users discover content on YouTube, such as on the YouTube homepage, search results, and related videos. They feature a thumbnail image from the video and some text, and advertisers are charged when viewers click on the ad to watch the video.


4. **Bumper Ads**: Bumper ads are non-skippable ads of up to 6 seconds that must be watched before the viewer's selected video can be played.


5. **Masthead Ads**: These ads appear at the top of the YouTube homepage and can provide massive visibility, but they are generally reserved for bigger advertising budgets and specific campaigns.


6. **Overlay Ads**: These are semi-transparent ads that appear on the lower portion of the video.


Google Ads allows advertisers to target their YouTube ads based on various criteria, including demographics, interests, keywords, and remarketing to reach specific audiences.


Keep in mind that Google often updates its advertising platform, so there might be new features or changes to the system beyond my last update in September 2021. For the most current information, it's best to visit the official Google Ads website or check with the Google Ads support team.