Market breadth indicates if a wider number of stocks are participating in the trend or it is being led by only a handful of names.A high breadth shows many stocks participating in an rally and hence it is healthier.
See the chart below:
The above chart shows the Advance Decline lines for NYSE, SPX, SP midcap and small caps. All the Advance Decline lines have hit new highs last week. This is very positive. It shows a large variety of stocks participating in the trend.
The above chart shows the % of stocks in the SP500 above their 200 day and 50 day moving averages. Note that the %of stocks above the 200 day MA has reached around 90. This means 90% of stocks in the SP500 are above their 200 day Moving Average. This is very bullish. It could also mean short term market is overbought but what is overbought can continue to remian overbought.
The conclusion is from a breadth perspective, the market is very healthy now.