Opinion-makers are people whose words change what a lot of other people think — politicians, journalists, TV hosts, and, these days, big online voices. The picture is that they do not only have an opinion; they help make the public’s opinion. You will meet the phrase in news and in writing about society more than in chat. Though actually, the tidy list “politicians and journalists” is the older picture. Younger speakers may reach for influencer, and in Taiwan people often say 意見領袖 or even KOL rather than a word-for-word “opinion maker.” Same kind of job, slightly different label. It is usually written with a hyphen (opinion-makers); the singular is opinion-maker. It does not have to mean they invent lies — though that unkind reading is easy to hear in the word make.