He was designed to help players navigate their way through the game. The Guide was dressed like a waiter, in a garish red shirt and jacket. He carried a clipboard with "Better Than Life" written on it.
He then met them at the restaurant, acting as Maitre d' and waiter. He served Lister with his Caviar Vindaloo and brought The Cat a small aquarium full of live fish - and a fishing rod.
Later, when Lister was thirsty while playing golf, The Guide was immediately there to provide him with a large, garish cocktail called a banana bomb. He lit the firework in the glass and watched it fly into the air. (RD: Better Than Life)