When given 3 points A B C in a Triangle
   \         /
    \  s·   /
     \   190m
     200m /
       \ /
The Steiner Point is the point within the triangle that connects the 3 corner nodes of the triangle into a Steiner Tree, and does so with the minimum overhead (in this case, distance).
This point is NOT equidistant from A, B, and C. Instead, angles ASB, BSC, and CSA are all 120 degrees. To easilly find this point, use Torricelli's Method of finding a Steiner Point.

10998521 is entirely correct in calling it the Fermat point. The Steiner Point is another alias, popularized by Courant and Robbins in What is Mathematics (1941), calling it the Steiner Minimal Tree problem.