Viscous flow refers to the movement of fluids that have a significant resistance to flow, often due to internal friction. This resistance is influenced by the fluid's viscosity, which is a measure of how thick or sticky a fluid is. For example, honey has a higher viscosity than water, meaning it flows more slowly. In viscous flow, the speed of the fluid can vary depending on the forces acting on it and the surrounding conditions. This type of flow is important in various applications, such as in the design of pipelines, lubricants, and even in understanding natural phenomena like lava movement.