Two-dimensional space refers to a plane space consisting of only two elements: length and width (X axis and Y axis in geometry), which only extends to the plane.
Three-dimensional space, in daily life, can refer to the space composed of three dimensions: length, width and height.
Four-dimensional space refers to the standard Euclidean space, which can be extended to n dimensions.
Four-dimensional space is different from three-dimensional space. Four-dimensional space refers to the standard Euclidean space, which can be extended to n dimensions. Four-dimensional space-time refers to a misunderstanding of Minkowski's concept of space. As a three-dimensional object, human beings can understand four-dimensional space-time (three spatial dimensions and one time dimension) but cannot recognize and exist in four-dimensional space, because human beings belong to the third spatial dimension. Generally speaking, time is the fourth dimension, that is, the time dimension in four-dimensional space-time. The fourth dimension of four-dimensional space refers to the space dimension with the same properties as X, Y and Z, but the four-dimensional space-time is not a standard Euclidean space, and the essence of time is to describe the speed of motion.
Through the evolution of one-dimensional, two-dimensional and three-dimensional space, people have put forward some conjectures about four-dimensional space. Although these conjectures can't be proved to be correct yet, many scientific theories begin with conjectures. Nowadays, scientific theories are generally based on summarizing the laws of phenomena, but there is not enough accurate and clear understanding of the phenomena in four-dimensional space, or we did not think that this phenomenon was caused by four-dimensional space after seeing it.
You can define that anything that can be measured can have dimensions. For example, points, lines, surfaces, time and temperature can form a five-dimensional space in a meaningful way.
Of course, the topological space of points, lines and surfaces can also be defined as the fourth dimension, the fifth dimension, the sixth dimension or even the nth dimension. This is easy to realize in mathematical formula reasoning, but it is difficult to correspond and imagine in reality.