Answer: The term "unit square" refers to a square with sides that have a length of one unit. By convention, the unit used is often determined by the context of the problem or measurement being made. For example, if we are measuring the area of a rectangular field in feet, we might use a unit square that is one foot by one foot, or 1 square foot. If we are measuring the area of a room in meters, we might use a unit square that is one meter by one meter, or 1 square meter.
The term "square unit" is used to refer to the units used to measure area. So, when we say that the area of a field is 120 square feet, we mean that the area can be divided into 120 unit squares, each with an area of 1 square foot.
Using unit squares to measure area allows us to easily compare the sizes of different areas and to perform calculations involving area. For example, if we want to find the area of a triangle, we can divide the triangle into smaller shapes (such as rectangles or triangles) and then count the number of unit squares needed to fill those shapes. We can then add up the areas of the smaller shapes to find the total area of the triangle, all in square units.