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Converging lenses, often referred to as convex lenses, have a distinctive shape that sets them apart. They are thicker in the middle compared to their edges. This unique shape is crucial to their function. When a beam of parallel light rays passes through a converging lens, these rays are bent inwards. This bending causes the rays to meet at a point. This point where all the light rays converge is called the focal point.
Converging lenses are used in many practical applications, such as in magnifying glasses, cameras, and corrective eyewear for farsightedness. Their ability to focus light makes them invaluable in various optical devices.

Diverging lenses, also known as concave lenses, have a shape opposite to that of converging lenses. They are thinner in the middle and thicker at the edges. This design causes light rays that pass through the lens to spread out. Imagine parallel light rays hitting a diverging lens; after passing through, the rays diverge as if they were emanating from a common point behind the lens. This point is known as the virtual focal point.
Diverging lenses are commonly used in devices like peepholes in doors and in glasses for people with myopia (nearsightedness). Their ability to spread light is essential in reducing the focus point of divergent light rays.

Light behaves differently when it encounters various types of lenses. The behavior of light when passing through a lens is influenced by the lens's shape and material.
When light passes through a converging lens, the rays are bent towards each other. This is because of the lens’s thicker center. The process of bending light rays is known as refraction. On the contrary, when light passes through a diverging lens, the rays spread out. The thinner center of the diverging lens causes this outward spread.
Understanding light behavior is crucial for designing optical instruments and for practical uses like vision correction, where precise control of light's direction is needed.

The concept of the focal point is essential when discussing lenses. The focal point is where light rays meet or appear to meet after passing through a lens.
In the case of converging lenses, the focal point is real. This means that the light rays physically converge at this point. In diverging lenses, the focal point is virtual. Although the rays appear to diverge from this point, they do not actually meet.
Knowing where the focal point lies helps in understanding how lenses focus or disperse light. For instance, in cameras, the lens’s focal point must align with the film or sensor to create a clear image. Similarly, in eyeglasses, the focal point adjustment provides clear vision to the wearer.