Lantern

A lantern is basically a lamp that a person can carry around. Usually, it is runy by some kind of fuel, most often oil-related products, and the flame is enclosed in a glass housing to protect it from the wind and weather. Such a lightsource usually is more reliable than the more primitive torches and gives more light than candles. As a rule, lanterns have to be regularly re-filled in order to stay operable.

Lanterns first appeared in Ultima Underworld as the strongest non-magical lightsource, a role that they also had in Ultima Underworld II. Interestingly, lanterns weren't encountered in the overworld until Ultima IX, where they interestingly enough didn't need to be refueled any longer.

Lamp Posts
Lamp posts essentially are a bigger an immobile variant of the lantern, used to shed light on the streets during the nighttime. Lamp posts were first encountered in Britannia during the time of Ultima V. These lamps were always lit, a fact that only changed in Ultima VII, when the lamp posts were outfitted with ignition mechanisms that the city guards with activate in order to light the lamps at dusk.

Lamp posts were also known on the Serpent Isle and on Pagan. Serpent Lamps are a special kind of lamp posts, lit with mixed chemicals instead of oil.

Trivia

 * In both parts of Ultima Underworld, the spell Mend can replace lamp oil, as it can be used to re-fill a lantern to full capacity.