During The Golden Age of Piracy, pistols and other firearms were everything but perfect, although they were used since mid 1400s. The Most of them fired only single shot and it took a long time to reload. They were also very inaccurate and did not have a long rage. In battles on board it would be impossible to fight with gun only.
Any successful pirate would carry more then one pistol in addition of some sword or dagger in order to survive. Still guns became invertible part of almost every pirate and every ship battle in the 17th and 18th century. There are many different types of pirate pistols can be short enough to fit in pocket or long as muskets.
This model of pistol is most used by pirates. It is a small and swift light gun based on the flintlock mechanism( replaced matchlock and wheellock technologies). Pistol size proved to be a pretty handful in boarding attacks as pistol could be easily tied to belt, and some pirate could wore a lot of them, like Blackbeard, who had six. Flintlock pistol was developed in France in early 1600s. Main disadvantage is that it was particularly hard to load.
This type of pistol usually has between two and four barrels, but each barrel was fired separately. It was also based on flintlock mechanism. There were two versions of this model: first and the most common version was with each barrel have its own firing mechanism. However, there were multi-barreled pistols that used only one firing mechanism on two or more rotating barrels. Multi-barreled pistol was an expansive weapon that was privileged just for the rich commanders. Another reason pirates did not often used it was pistols slow and heavy.
Just like multi-barreled pistol, volley pistol had more then one barrel. However, volley pistols fired all barrels simultaneously. Volley pistol were expensive, hard to keep and just like any other gun with more then one barrel was pretty inaccurate at longer range. Still, the idea of volley pistol was innovative and used for some modern projectile weapons.
Just as name says, pocket pistol is the smallest pirate fire weapon. Just like daggers, pocket pistols were a weapon of surprise attack. They were easily concealed, quickly drawn and deadly. Those advantage automatically made them pirate appreciated. They were single shot weapon based on flintlock mechanism.