what is drawing manager in google maps code example

Example: how to change drawing tool color google map

// This example requires the Drawing library. Include the libraries=drawing
// parameter when you first load the API. For example:
// <script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=drawing">
function initMap() {
  const map = new google.maps.Map(document.getElementById("map"), {
    center: { lat: -34.397, lng: 150.644 },
    zoom: 8
  });
  const drawingManager = new google.maps.drawing.DrawingManager({
    drawingMode: google.maps.drawing.OverlayType.MARKER,
    drawingControl: true,
    drawingControlOptions: {
      position: google.maps.ControlPosition.TOP_CENTER,
      drawingModes: [
        google.maps.drawing.OverlayType.MARKER,
        google.maps.drawing.OverlayType.CIRCLE,
        google.maps.drawing.OverlayType.POLYGON,
        google.maps.drawing.OverlayType.POLYLINE,
        google.maps.drawing.OverlayType.RECTANGLE
      ]
    },
    markerOptions: {
      icon:
        "https://developers.google.com/maps/documentation/javascript/examples/full/images/beachflag.png"
    },
    circleOptions: {
      fillColor: "#ffff00",
      fillOpacity: 1,
      strokeWeight: 5,
      clickable: false,
      editable: true,
      zIndex: 1
    }
  });
  drawingManager.setMap(map);
}