Here's why:
* Proper nouns are specific names of people, places, or things. They are always capitalized. Examples include:
* People: John Smith, Queen Elizabeth
* Places: Paris, Mount Everest
* Things: The Great Wall of China, The Eiffel Tower
* Common nouns are general names for people, places, or things. They are not capitalized unless they start a sentence. "Furniture store" is a common noun because it describes a general type of store.
Examples:
* Proper noun: "I went to IKEA to buy a new sofa." (IKEA is a specific furniture store)
* Common noun: "I went to the furniture store to buy a new sofa." (This refers to any furniture store)