What is the difference between a direct-blowing cooling fan and a side-blowing cooling fan?

Our commonly used cooling fans mainly come in two forms, one is a direct-blowing cooling fan, the other is a side-blowing cooling fan, as shown in the figure below, the left and right are direct-blowing 4010 cooling fans, and the right side is the side-blowing cooling fan. What is the difference between the type of cooling fan? The wind direction is different, the direct-blowing type cooling fan takes in the wind from the top and the wind from the bottom. The side-blowing type is for air intake from above, and the side-blowing type of heat dissipation fan generally blows air, such as a CPU fan. The side-blowing type of heat dissipation fan is a direct-blowing type of heat dissipation fan with large air volume, low air pressure and noise. Low, the opposite of the blowing side, the material cost and labor cost of the same size direct blowing type are a little lower