Assuming that I have a point on a map and a multipolygon on a map. When I query with
ST_Within I get the same result. I want to know what is different between these two methods?
PostGIS is well documented. Doing some research gives you following results.
ST_Intersects: https://postgis.net/docs/ST_Intersects.html If a geometry or geography shares any portion of space then they intersect.
ST_Within: https://postgis.net/docs/ST_Within.html Returns TRUE if geometry A is completely inside geometry B
For points, there is no difference. When it is inside the polygon, it also shares a portion.
On the other hand, when you do the same with lines. A line that is not entirely within the polygon will not be selected with st_within.