Assertiveness is a healthy communication style that allows people to express their needs and wants while also listening to others. Passive communication does not allow people to have their needs met, while aggressive communication is one-sided and can damage relationships. Assertive communication involves standing up for oneself and others, using "I" statements honestly while also listening, and finding solutions. Being assertive takes practice but has benefits like gaining respect, resisting pressure, feeling good about oneself, and getting needs met without hurting others.