Minimap

The minimap is a HUD element that represents the entire map on a smaller scale. It displays in real time the location and status of structures (green for Radiant and red for Dire) and the current location of all Heroes within sight range, as well as lane creeps, neutral creeps, and Roshan. Heroes in the minimap are usually represented by spheres with a pointy arrow (for allies) or a cross (for enemies). By holding Alt, you can change these icons so they display a small image of the Hero they represent, this feature can also be made permanent in the Options menu. While in the game, the minimap also displays sight range and fog of war for your whole team.

Pinging
Holding down Alt and clicking on the minimap will "ping" all allied players. A colored circle with an exclamation point will appear at the location pinged, both on the minimap and on the main map. Also, a noise will sound. The pitch of the noise and the color of the circle correspond to the color of the player's name. If the ping is centered on an allied tower, a shield will be displayed there on the minimap. If the ping is centered on an opposing tower, a sword will be displayed there. If the ping is centered on a rune, then the the rune type will be shown in allied team chat.

Drawing
Holding down both Ctrl and the left mouse button while moving your cursor over the minimap will draw lines on the minimap. These lines can be seen by all allied players, and their color corresponds to the color of your name.