The particles that make up a solid are very ordered, and the forces between the particles are strong, holding the particles in a rigid form. A solid cannot flow (freely move).
Gas particles have no regularity in their arrangement. Gases have no restrictions on their movement, and are widely separated. The forces between gas particles are small, which allows the particles to move apart and fill the available space. Gases flow, thus gases are fluids (materials that flow).
Liquid particles have less energy than gases and more energy than solids. While they are not as free in motion as are gases, they can move in respect to each other. When pressure is applied, the liquid molecules flow. Because of this, when a surface is wet with a liquid, such as water, the surface can be slippery. Liquids, like gases can flow, thus liquids are fluids.
The signs shown indicate that when walking on a wet surface, you might slip and fall. The particles of liquid under your feet move when your foot presses on them. The same thing can happen when driving on a wet surface. Cars are often said to ” hydroplane” if the water is very deep. This means that your tires are no longer in direct contact with the road, instead they are riding on top of the water that has pooled on the road. This is a very helpless feeling because the driver is no longer in control of where the car is going.