What is common and how do unicellular, multicellular and colonial organisms differ?

The general fact is that they all consist of cells (or one cell) and represent a single whole, with its characteristic mechanisms for the coordinated functioning of its organs (organelles, groups of cells) in the process of life.
They differ in that a unicellular organism consists of one cell, a multicellular organism consists of many cells, and a colonial organism is a colony — a group of weakly differentiated cells that are not divided into tissues.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.