This chapter discusses relationship dynamics and development. It explains that positive relationships are important for well-being, and relationships vary in significance from strong to weak ties. Relationships have benefits and drawbacks, and are governed by both implicit and explicit rules. Relationships progress through stages from initial attraction to maintenance based on evaluating rewards versus costs. Managing self-disclosure and reducing uncertainty are important for developing relationships. Dialectical tensions around issues like connection and autonomy must also be effectively addressed to maintain healthy relationships.