A one-piece toilet and a two-piece toilet are two different designs of toilets, distinguished primarily by the number of separate components they consist of.

1. One-Piece Toilet: As the name suggests, a one-piece toilet is constructed as a single, integrated unit. It comprises a seamless combination of the tank and the bowl, meaning there is no visible joint or seam between the two. The tank and bowl are fused together during the manufacturing process. One-piece toilets generally have a sleeker and more compact appearance, as they lack the distinct seam between the tank and bowl found in two-piece toilets. They are also usually easier to clean because there are no gaps or joints where dirt and grime can accumulate. However, one-piece toilets can be heavier and more challenging to install due to their single-piece construction.
2. Two-Piece Toilet: A two-piece toilet consists of two separate components: the tank and the bowl. The tank is usually mounted on top of the bowl with bolts and a gasket to form a secure connection. Two-piece toilets are more common and traditional in design. They have a visible seam between the tank and the bowl, which can collect dirt and require more effort to clean compared to one-piece toilets. However, two-piece toilets tend to be more affordable and easier to transport and install due to their separate components.

In terms of functionality, both one-piece and two-piece toilets operate in the same manner and offer similar features such as flushing mechanisms, water-saving options, and different bowl shapes. The choice between the two depends on personal preferences, budget, ease of installation, and desired aesthetics.