This meta-tag appears in your browser at the very top left of the screen, alongside your favicon. It can be amended by an SEO plugin to fill the recommended number of characters of 60.

This tag is very important to search engines as:

• • 1. it is visible to the visitor, and
    2. it ostensibly sums up the purpose for the page.

Other meta-tags are largely ignored by search engines where they are not visible to a visitor. E.g. keywords meta-tags are ignored.