A manipulator, in the sense you are learning, is a person who is skilful at getting what they want by steering other people — with charm, pressure, half-truths, or by playing with feelings — rather than by asking in a straight way. It is a cold word. If you call someone a manipulator, you are saying they treat people like pieces in a game. Newspapers, offices, and talk about relationships use it this way. Though actually, the same spelling also names a machine arm that moves things, and in older English it could just mean someone with clever hands. In ordinary talk today, though, especially about people, it almost always carries that unkind meaning. It is stronger than “persuasive” and darker than “clever.” A good teacher or a kind parent may guide you; a manipulator hides the guiding.