The close is the last price that traded during a chart period. On a one day candle, it is the final price when the day ended. It is one of the four prices in OHLC and is the value most line charts plot because it is often treated as the period's settled price.
Many traders weigh the close heavily because it reflects where price settled after all the back and forth.
The app files could not be fetched. This is usually a network hiccup or an out-of-date cached copy of the site.