Six cyanide ions are bound to an iron(II) ion. In the name, hexa means six ligands and cyanido means the ligand is the cyanide ion. The potassium salt is potassium hexacyanidoferrate(II), also known as yellow prussiate of potash.
The coordination number is 6 and the geometry is octahedral. The six directions around the iron are up and down, front and back, left and right, each 90 degrees from its neighbours. Every ligand binds through its carbon, with the nitrogen beyond it held by a triple bond.
The solution is pale yellow. Adding iron(III) to it gives a deep blue precipitate, which is used as a test for iron(III). That precipitate is Prussian blue.