A freezer is typically a compartment within a refrigerator, not a separate appliance, though it can also be a standalone unit. In most modern household refrigerators, the freezer occupies the upper or lower section and is insulated to maintain temperatures at or below 0°F (-18°C), while the refrigerator section stays between 35–38°F (1.7–3.3°C). The two compartments share cooling systems and are housed in the same cabinet.
However, many people also own separate chest freezers or upright freezers as independent appliances, stored in basements, garages, or kitchens. These function independently from a refrigerator. Some households have both a refrigerator-freezer combination and an additional standalone freezer for extra storage.
So the answer depends on context: if you're asking about a standard refrigerator unit, yes, the freezer is built into it. If you're asking whether all freezers are part of fridges, the answer is no—standalone freezers are common and separate appliances. The term "fridge" typically refers to the entire refrigerator unit (including any built-in freezer), while a "freezer" can mean either the freezer compartment within a fridge or an independent freezing appliance.