If you are Googling this phrase to find a free copy of modern Illustrator, or to download the old version from a third-party site, please read this safety and legality review carefully.
The short answer is . Adobe has never officially released Illustrator 10 as "freeware." The "CS2" Misconception
: It was the last standalone "numbered" version (v10) before version 11 became Illustrator CS Standardization