A lawmaker is a person whose job is to make the laws — usually someone people voted for, who sits in a parliament, a congress, or (in Taiwan) the Legislative Yuan. News English likes this word because it covers many titles at once: senator, MP, legislator. In daily talk you more often name the real job. Though actually, not every person people vote for is a lawmaker: a mayor mostly runs a city; a president may sign laws but does not always write them. “Lawmaker” points at the writing-and-voting part, not at the police and not at a lawyer who argues in court. It is a newspaper word more than a playground word, and it is not slang.