Meaning: This sentence states that apples can be found in a variety of different forms.
Choice of Words: "They" refers to the apples. "Come" is a verb that means to arrive or appear. "In" is a preposition that indicates the location of the apples. "All" is an adjective that means every or any. "Shapes" is the object of the preposition and refers to the different forms that the apples can have.