The Australian Share Market, as represented by the S&P/ASX200 index, is divided into 10 Global Industry Classification Sectors (GICS Sectors). These 10 sectors in turn represent 24 industry groups, 67 industries and 147 sub-industries.
Reviewing the performance of industries or sectors fits somewhere in the middle of the 'top down' approach to investing (that is, you pick your investments by looking first at the broad macroeconomic outlook and work your way down to finish with the individual security analysis last).
While stocks from the same industry will be impacted by different factors from time to time, they will also be impacted by factors that affect all industries or sectors. Generally, the share price performance of stocks within a sector will have a high degree of correlation.