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Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with the increasingly common convection feature (which uses a fanfans to circulate the air around the oven to get more even cooking(commonly called "convection ovens").

Professional bakeries will use a professional oven that evenly distributes the heat and/or automatically rotates the trays, thus not requiring manual swapping or rotation of the trays.

Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with the increasingly common convection feature (which uses a fan to circulate the air around the oven to get more even cooking).

Professional bakeries will use a professional oven that evenly distributes the heat and/or automatically rotates the trays, thus not requiring manual swapping or rotation of the trays.

Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with fans to circulate the air (commonly called "convection ovens").

Professional bakeries will use a professional oven that evenly distributes the heat and/or automatically rotates the trays, thus not requiring manual swapping or rotation of the trays.

2 Clarified the rotation aspect per @AdamDavis's comment.
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Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with the increasingly common convection feature (which uses a fan to circulate the air around the oven to get more even cooking).

Professional bakeries will use a professional oven that evenly distributes the heat and/or automatically rotates the trays, thus not requiring manual swapping or rotatingrotation of the trays.

Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with the increasingly common convection feature (which uses a fan to circulate the air around the oven to get more even cooking).

Professional bakeries will use a professional oven that evenly distributes the heat, thus not requiring swapping or rotating the trays.

Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with the increasingly common convection feature (which uses a fan to circulate the air around the oven to get more even cooking).

Professional bakeries will use a professional oven that evenly distributes the heat and/or automatically rotates the trays, thus not requiring manual swapping or rotation of the trays.

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Swapping and rotating baking trays is recommended in order to account for differences in temperature inside residential ovens. Typically, the top of the oven is significantly hotter than the bottom. This is less of a concern with modern ovens, particularly those with the increasingly common convection feature (which uses a fan to circulate the air around the oven to get more even cooking).

Professional bakeries will use a professional oven that evenly distributes the heat, thus not requiring swapping or rotating the trays.