Since you’re an Historian, I quess you’re the right person to ask :) ASOIAF is full of seafaring vocabulary; since I prefered to read all the series in the original language I could never figure out the different sizes and shapes of all the different ships cited in it (although, I reckon that even if I read them translated, I still couldn’t picture them in my mind to tell the truth…) What’s the difference between a galley/galleas/cog/carrack/etc.?

Good question!

A galley is a ship primarily powered by rowing, tends to be rather long and narrow with a relatively shallow draft. Galleys were the dominant seacraft in the Mediterranean from the classical era through to the 16th century, especially in the era before gunpowder weapons where naval combat focused on ramming and boarding. 

A galleas is a heavier galley – they were higher on the sides, they were longer than galleys, and they were slower. They also tended to have more masts and thus more sails than galleys, relying less on oarpower (although they had oars) in order to use the saved space for gun-decks, which meant that they could pack a lot more firepower than a galley. In a sense, the galleas is a transitionary ship between the pre-gunpowder era and the gunpowder era of naval combat.

A cog is a sailing ship without oars, that emerged in the 10th century in the Baltic. Cogs are made from oak, have a single mast, and a square sail. They’re small ships designed for ocean-going commerce, not warships. 

Carracks are larger sailing ships than cogs, with three or four masts, which were perfected by the Portugese in the 15th century. With more sails than the cog, you can sail a bigger ship faster, which made the carracks excellent for long sea-voyages and long-distance commerce, because their larger holds allowed you to carry more goods and supplies. When you think about the voyages of Columbus or Magellan, you’re thinking about carracks.