When you put two things right next to each other, you can call that apposition. The apposition of your dog and your cat makes an adorable photograph.
Though you can use the noun apposition to talk about the positioning of objects — or words — close together, it's usually found in scientific or technical writing. In grammar, an apposition occurs when two words or phrases are placed beside each other in a sentence so that one describes or defines the other. An example is the phrase "my dog Woofers," in which "my dog" is in apposition to the name "Woofers."