This is going right down the SEO rabbit hole, but Google has announced changes to the way it interprets the ‘nofollow’ attribute on links. Don’t worry if that means very little. Basically, if you’re using ‘nofollow’ to control the way your website is crawled, you may need to rethink the strategy, and if that doesn’t mean much, you can probably ignore this.
Using ‘nofollow’ on links has traditionally told Google not to look at the page being linked-to, and not to pass on credit to that page for ranking purposes. You can read more about it at an good, older article like this. Links from Wikipedia, for example, will have the ‘nofollow’ attribute, so you don’t get lots of ‘link juice’ from being quoted there.
There seem to be two elements to the announcement. The first is that Google now treats the nofollow attribute as a “hint” for ranking purposes, rather than a rule, and will next year do the same for crawling and indexing purposes. The second is that there are now three different types of nofollow attribute, designed to explain why you’re making the recommendation: these are “sponsored” (e.g. advertisements), “ugc” (User Generated Content, such as comments and forum posts) and “nofollow” (the traditional no-endorsement link). Paid links should either use the nofollow or sponsored attribute.
The important thing to understand is that you don’t need to change anything, but if you have some fairly sophisticated SEO in place on your site, you may want to discuss this with whoever put it in place.