Google announces two new link attributes that provide webmasters with additional ways to identify to Google Search the nature of particular links.
rel="sponsored": Use the sponsored attribute to identify links on your site that were created as part of advertisements, sponsorships or other compensation agreements.
rel="ugc": UGC stands for User Generated Content, and the ugc attribute value is recommended for links within user generated content, such as comments and forum posts.
rel="nofollow": Use this attribute for cases where you want to link to a page but don’t want to imply any type of endorsement, including passing along ranking credit to another page.
Do I need to change my existing nofollows?
No. If you use nofollow now as a way to block sponsored links, or to signify that you don’t vouch for a page you link to, that will continue to be supported. There’s absolutely no need to change any nofollow links that you already have.
Can I use more than one rel value on a link?
Yes, you can use more than one rel value on a link. For example, rel="ugc sponsored" is a perfectly valid attribute which hints that the link came from user-generated content and is sponsored. It’s also valid to use nofollow with the new attributes -- such as rel="nofollow ugc" -- if you wish to be backwards-compatible with services that don’t support the new attributes.
Read more on Google's Webmaster Central blog