v5 specific questions on the OpenLayers mapping library
OpenLayers v5 is the latest release of the OpenLayers mapping library.
From https://openlayers.org/:
OpenLayers makes it easy to put a dynamic map in any web page. It can display map tiles, vector data and markers loaded from any source. OpenLayers has been developed to further the use of geographic information of all kinds. It is completely free, Open Source JavaScript, released under the 2-clause BSD License (also known as the FreeBSD).
v5 reworked the library as a set of ES Modules, and improved compatibility with mainstream module bundlers.