Definition - What does Google Toolbar mean?
To a certain extent, the Google Toolbar is obsolete. It was created in a time when browsers didn't have built-in search. Pretty much any modern browser, including Chrome, allows direct searching on Google or other search engines without an add-on.
Techopedia explains Google Toolbar
One reason for its continued popularity is the ability to get the Google PageRank for the current site. Many in SEO have the Google Toolbar for this purpose even though they don't need the other functionality.