Assertiveness is a communication style that involves openly expressing one's thoughts, feelings, and needs while also respecting others. It is distinguished from aggression, which does not respect personal boundaries, and passivity, which involves not standing up for oneself. Becoming more assertive can improve relationships and reduce stress by helping people get their needs met while also respecting others. Learning assertiveness skills involves honestly evaluating one's own communication style, developing a cooperative mindset, and practicing expressing oneself clearly and respectfully.