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Almost all the functions in PostGIS start with ST. e.g. ST_Distance_Sphere, ST_GeomFromText, ST_Intersection, etc.
What does ST mean?
http://www.postgis.org/documentation/manual-svn/PostGIS_Special_Functions_Index.html
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Saint (St or St.), especially in Christianity. Scheduled Tribes, in India. Ship prefix for a steam tug. Sine tempore (s.t.), Latin term indicating that a lecture will begin at the exact time; see Academic quarter (class timing)
The ST_Intersects() function returns t (TRUE) if the intersection of two geometries does not result in an empty set; otherwise, returns f (FALSE).
geometry is a fundamental PostGIS spatial data type used to represent a feature in planar (Euclidean) coordinate systems. All spatial operations on geometry use the units of the Spatial Reference System the geometry is in.
PostGIS = very fast. Barcharts don't lie. As you can see from the graph earlier, it took PostGIS less than 10 % of the time to do the same analysis compared to QGIS and a Shapefile. If you are a GIS analyst and do processes like this every day, that can save you quite a lot of time in a year.
From the manual:
PostGIS has begun a transition from the existing naming convention to an SQL-MM-centric convention. As a result, most of the functions that you know and love have been renamed using the standard spatial type (ST) prefix. Previous functions are still available, though are not listed in this document where updated functions are equivalent. These will be deprecated in a future release.
Hope that helps.
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