What term describes a group of cells with similar structure and function plus extracellular substance?

The term that describes a group of cells with similar structure and function, along with their extracellular substance, is "Tissues." Tissues are the building blocks of organs and are made up of cells that work together to carry out a specific function. For example, muscle tissue consists of muscle cells that enable movement, while connective tissue supports, binds together, and protects other tissues and organs.

In contrast, the other options refer to different biological structures. "Organs" are composed of different types of tissues working together to perform complex functions, such as the heart or liver. "Systems" are groups of organs that work together to perform complex activities, such as the cardiovascular or nervous systems. "Cells" are the smallest structural and functional units of life, but they do not encompass the grouping indicated in the question. Thus, tissues are the correct answer as they represent the specific aggregation of similar cells and their extracellular matrix.