A pike is a long (3-6.5 metre), pointed stick used en masse to keep an advancing force at a distance. The idea originally came from spears, (this is why Roman spears were so long). From the age of Alexander up until the practicality of black powder weapons, the pike was very popular. The pike had been an infantry’s weapon of choice against cavalry. Typically, a pike would be used by every man in the first three (give or take) rows of infantrymen. The pike was held about at a 20° angle to keep horses from jamming through the lines. With this three row deep defense, one could safely bring out archers. Archers were always a prime target, because their weapons were not those of close quarters combat, and they had usually no armor. If you were an archer, pikes are your friend.

The pike was extremely useful in wickedly smiting forward advancing heathens, but if you got flanked...dizamn. Pikes were quite the immobile weapon, and hinders the fluidity of your forces. That's their only real pitfall, as far as I can tell.

Note: If you've seen Braveheart, then you've seen pikes. Remember when they hid those big ass sticks when the horsies were advancing, then when they got real close, skewered them? Those were poles were an example of pikes.