보다

than, in a comparison

Goes on the thing being beaten to set up a comparison: 생각보다 시간이 많이 걸리네요 is "it's taking longer than I thought", 대통령보다 더 바빴다 is "I was busier than the president", 한국보다 6시간 느린 is "six hours behind Korea". Korean puts the yardstick first, so the order is the reverse of English. 더 ("more") often follows but is not required. Note the spelling trap: this is unrelated to the verb 보다, "to see", which looks identical — here it always leans on the noun right before it.