If you are a believer in Dow Theory, todays close is a very important pivot point. According to Dow Theory there are 2 possible outcomes from here.
If 2 of the indexes continue to move up and close above the previous bull market highs (4,537 S&P, 35,625 Dow, 15,943 Dow Transports), the bull market is confirmed moving forward and this secondary reaction is concluded.
If 2 of the indexes fail to make new highs and break down and close below its last secondary reaction (4,300 S&P, 33,844 Dow, 14,000 Dow transports) its bear market time.
Obviously, the original Dow Theorist (Charles Dow, who developed the DJIA in 1896) compiled his theory on the DJIA and Dow Transports only, but modern interpretations include the S&P 500.
Just another set of data points to consider as we all try to figure out which direction the market is going to move.