Treasure Map is an item that can be solved by a riddle. When solved you get a Treasure Chest. It can be found with Pirate, Boats or Monster Loot. There are three types of maps: normal, Green Map and Red Map. The map appears in the Item tab and the player can have only one at a time. It is however possible to have one normal map, one green map and one red map at a time.
After receiving the Runite Spyglass as a reward from the Pirate's Treasure quest, the pirates start looking for Green Treasure Map, in addition to normal Treasure Maps. The green version gives you a Green Treasure Chest, which gives better loot and far better chances to get Green Orbs than the normal chest.
Pirate has a fixed chance of getting maps based on the number of pirates purchased, while the chance to get a map from boats is very rare (estimated: 1/100 to 1/300). The chance from loot bags varies by areas. Loot bags from Fields have 1/500 chance to get a map, goes up to 1/400 for Forests and 1/300 for the rest of areas.
The rarity of a Green map is twice as high as regular maps. With one pirate their discovery chance is 1 in 600k every second. With 10 pirates, the discovery chance is 1 in 400k every second.