What is meant by stock market showing very high index? For what quantity does it show a high index? Please explain this.
For each major stock exchange there is typically an index that is more or less representative of the level of the stock market trading at that index: Dow Jones, Nasdaq 100, S&P500, FSTS100, Eurostoxx, etc Such an index can be computed using various methods such as price average (Dow Jones), market cap weighting (S&P 500), etc. with dividends (DAX) or without them (every other major index). Quite often such an index will show an all-time high which creates headlines in the media. The next day, this "all time high" will often be surpassed by yet another ATH
Just look at the following graph. It shows in red when the S&P 500 had yet another all time high and how meaningless those were in historic retrospective. An ATH only becomes meaningful if there is a major drop afterwards, if not it is just a part of a general rise of the stock market (source)