Hi Teht,
If you select the "Map" option from the "Tools" menu (or CTRL+M for short) it will open the large map window. On the bottom left hand side of the window you will see a blue questionmark icon. Place your mouse over it and a popup will explain what the marks are. Wherever you see the same questionmark icon means there is popup help/information available.
To answer your question here, there are 3 different symbols used on the maps. This is so that you can tell the height the avatar is at in 3 levels:
* Green dot - same level as your avatar
* Red triangle - 20 metres and over below your avatar
* Blue square - 20 metres and over above your avatar
The yellow circle with red border is your avatar.