The Dire side icons are only used when observing a game. For players, the player's personal courier uses the Radiant style icons while allied and enemy couriers are shown as a green or white dot respectively.
On the minimap will alert your team about a location by ▶️ playing a sound and showing an ‼ Ping exclamation mark on their minimap.
On buildings will play a different sound depending on the building's alliance, and generally mean a ▶️ defense or ▶️ attack of the building is desired.
On enemy heroes will play the same sound as on enemy buildings, typically to announce the desire to attack.
Ctrl+Alt+ Left Click on the minimap will alert your team by ▶️ playing a different sound and showing an ✖ Ping (Danger) on their minimap, generally indicating danger.
Ctrl+ Left Click+⤓ Hold 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 the player. Lines will fade after a few seconds.
There are several console commands that can be used to modify the minimap in various ways to match an individual player's preferences. Some of the commonly used ones are shown below.
Use extra large minimap.
Changes the hero minimap icon size.
Minimum time after the mouse enters the minimap before accepting a move command. Can be increased slightly to prevent accidental misclicks.
Adjust how long pings are displayed on the minimap.
Disables right clicks on the minimap.
Increase the size of creeps/neutrals/roshan icons on the minimap.