In the spirit of better investing, and in celebration of the first annual Worldwide Invest Better Day (WWIBD) coming up on September 25, Motley Fool analysts will be answering user- and reader-submitted questions leading up to the big event. "Ask a Fool" anything, and we'll do our best to help you invest better.

The S&P 500 (INDEX: ^GSPC) is a capitalization-weighted index whose components are weighted by the total market value of outstanding shares. Because it's weighted this way, companies that are disproportionately larger -- like Apple (AAPL -0.59%) and Exxon (XOM 0.36%) -- have the most influence over the index, while those on the smaller end, like MAKO Surgical (MAKO.DL) and First Solar (FSLR -1.60%), have a much lower weighting. In the following video, Fool.com analyst Austin Smith goes over everything that investors need to know about the S&P 500.

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