They are all pretty much the same: referring to someone who reports the news. But journalist usually refers to a reporter for a newspaper, journal, or other written publication. Reporter and correspondant can refer to either a broadcast (tv, radio, vidéo, etc) reporter or a print reporter (newspaper, journal, Internet blogger, etc.)

Nothing, they all mean the same thing. However, "correspondent" is usually only used for writing, so that person would be a print reporter for a newspaper or magazine (not someone on TV or radio). Also, "newsman" is not very common anymore since it is considered sexist.

correspondent is a person who responds to a survey or a question given to him/her reporter, journalist and a newsman are pretty much the same :) they do the same thing such as write an article and report an event on tv