It's essentially a measure of risk and the typical range we can expect to see the price fluctuate up or down.

Say that VFIAX is trading at $50 at the beginning of the year. What is the range in which it will most likely finish the year?

Data in Picture -

$38.86 $61.14 $32.72 $67.28 $40.40 $59.60 $41.36 $58.64 Submit VFIAX VSMAX VBTLX Ticker Description S&P 500 Fund Small Cap Fund US Bond Fund 50% 30% 20% Allocation Historic Return 13.28% 11.28% 3.28% Expense Ratio 0.04% 0.05% 0.05% Standard Deviation 17.3% 22.3% 3.3% I

\begin{tabular}{|c|c|c|c|c|c|} \hline Ticker & Description & Allocation & Historic Return & Expense Ratio & Standard Deviation \\ \hline VFIAX & S\&P 590 Fund & 502 & 13.28% & 0,04% & 17.38 \\ \hline VSMAX & Seall Cap Fund & 30% & 11.288 & 0.058 & 22.3% \\ \hline VBTLX & US Bond Fund & 208 & 3.28% & 0.05% & 3.3% \\ \hline \end{tabular}