The term for a group of cells that perform a similar function is a tissue. Tissues are organized collections of specialized cells that work together to carry out specific tasks within an organism. Different types of tissues can be classified into four main categories in animals: epithelial, connective, muscle, and nervous tissue. In plants, primary tissue types include ground, vascular, and dermal tissues. Understanding the composition and function of tissues is essential for studying biology, physiology, and medicine.