Boy in gray shirt posing for a photograph .
A boy is in a gray shirt
Boy in gray shirt posing for a photograph.
A boy is in a gray shirt
In the first sentence it states there is a boy in gray shirt that is performing an action, the second sentence is just a general statement that a boy is in a gray shirt.
In the first sentence it states there is a boy in gray shirt that is performing an action , the second sentence is just a general statement that a boy is in a gray shirt .