Currency

Coins are the standard currency used in Tibia. The coins can be made of either gold, platinum, or crystal.

Each coin weighs 0.1 oz.

Gold Coins are dropped by almost every creature on Tibia.

Alternatively, you may see amounts followed by the letter k. This likely derives from the latin kilo-, meaning "thousand". For example "5k" means "5,000 gp" (equal to 50 platinum coins). The notation "1M" is often used to mean "1,000,000 gp" (100 crystal coins), however it is more common to see "1kk" (1000 times 1000) to represent "1,000,000 gp".

(Note: Amounts in the "one million" range are typically only mentioned in the context of selling extremely rare items or as a payment demanded in lieu of being hunted.)

You can exchange your coins at any Bank NPC around Tibia.

Tibia Economy
Because of certain safe-guards, inflation basically never occurs in the Tibian worlds. Instead, equipment tends to become cheaper over time as more and more of the stronger equipment is looted from creatures, while the value of runes usually remains somewhat static.

Abbreviations
Gold Piece (GP) or simply Gold

Platinum Coin (PC) or Plats, Platinums, P-Coin

Crystal Coin (CC) or simply Crystals