Inline brief description of implicit data structures

Author: vterron

[2018] Python Heaps-ters/python-heaps-ters.ipynb

@@ -1891,7 +1891,7 @@
     "# The alternative\n",
     "\n",
     "- Binary heaps can be represented in a very space-efficient way using **an array**.\n",
-    "- This is known as an [implicit data structure](https://en.wikipedia.org/wiki/Implicit_data_structure).\n",
+    "- This is known as an [implicit data structure](https://en.wikipedia.org/wiki/Implicit_data_structure) — the position of the elements carries meaning and relationship between elements.\n",
     "- We're *flattening* the tree...\n",
     "- ... and using a formula to move across nodes.\n",
     "\n",