Broad-Based Index

What Does Broad-Based Index Mean?
An index designed to reflect the movement of the entire market. The smallest broad-based index is the Dow Jones Industrial Average with 30 industrial stocks and the largest is the Wilshire 5000 Total Market Index. Other examples include the S&P 500, Russell 3000 Index, AMEX Major Market Index and the Value Line Composite Index.

Investopedia explains Broad-Based Index
Investors who want the maximum benefit of diversification can invest in securities that have as their underlying tracking instrument an index or other financial product made up of several, well-diversified stocks. Securities based on broad-based indices allow investors to effectively own the same basket of stocks contained in a major index while committing a small amount of financial resources.