The "index, follow" and "use global" directives are both used in the "meta-robots" tag to provide instructions to search engine crawlers. However, there is a key difference between the two.

The "index, follow" directive tells search engine crawlers to index the web page and follow the links on that page to discover and crawl other pages on your website. This directive is used when you want search engines to include your web page in their search results and to also follow the links on that page to discover and crawl other pages on your website.

On the other hand, the "use global" directive tells search engine crawlers to use the instructions provided in the global "meta-robots" tag for the entire website. This means that the "use global" directive will inherit the instructions provided in the global "meta-robots" tag, which may include different directives such as "noindex" or "nofollow". This directive is used when you want to apply the same instructions to all pages on your website, without having to specify the instructions on each individual page.

In summary, the "index, follow" directive is used when you want to provide specific instructions for a single web page, while the "use global" directive is used when you want to apply the same instructions to all pages on your website by inheriting the instructions from the global "meta-robots" tag.