While the characters are Chinese originally, they're most likely the Japanese versions of the characters. Japan and Korea have a... complicated (that's putting it nicely) relationship. Japan occupied Korea and forced them to learn Japanese. Japanese uses Chinese characters and so while not everyone learns Japanese anymore, that bit of the writing system has held on.

And while in Chinese most characters have only one (I believe) reading, in Japanese the characters often have multiple. Usually they at least have an on-yomi (Chinese reading based on how that character is read in Chinese) and kun-yomi (a native Japanese reading). Many of the characters were actually borrowed from Chinese more than once and so gained multiple readings (the readings had changed in China). Plus because of the complicated way the characters have been used in Japanese, they often have more than one Japanese reading as well.

Also, there are THOUSANDS of Chinese characters so you can definitely expect there to be some overlap in pronunciation.