Mr. Giles is the butler/steward at Mrs. Maylie’s house. This is an odd position: he’s a servant, but he’s kind of at the top of the servant social ladder. (19th Century English Lit pro-tip: Servants are often some of the most interesting characters in Victorian novels, because of what they show about the social hierarchy.)
Giles gets his own room and office, and can eat by himself there if he wants to (instead of eating meals with the other servants in the kitchen). But the problem is that it’s lonely at the top. So Giles hangs out in the kitchen with the other servants, but only on the understanding that he’s doing them a favor by gracing them with his presence. He’s pompous and arrogant, but in a harmless way. He likes to feel important, and Mrs. Maylie likes to humor him. He’s completely devoted to Mrs. Maylie and Rose. Despite being all proud of himself for having "caught" Oliver when he appears, bleeding, on their doorstep, a word from Rose has him caring as gently for Oliver as if he were a nurse.