A 4K Ultra HD TV screen is made up of 3840 x 2160 pixels - that’s 4x the number of pixels compared to Full HD. Owners find 4K TVs impressively stimulating, with the most vibrant colours and sharp imagery thanks to a slew of sophisticated colour and backlighting technologies (depending on model and price point).
Like Full HD, some smaller TVs are 4K, like these 43” Sony or Samsung 4K TVs, however if you’re looking at going big - with a screen of at least 55” to a whopping 85” - the resolution is always 4K (and increasingly 8K) because Ultra HD at that scale is simply better.
With 4K, there’s also different screen technologies to choose from: OLED (the best picture quality), LED LCD (the most common type), QLED (tiny quantum dots magnify brightness and colour using a backlight made up of LEDs), or Mini LED (new LED LCD TVs offering superior contrast and brightness over conventional LED TVs). Full HD TVs are generally LED LCD.
You can stream 4K Ultra High Definition (UHD) content on a Full High Definition TV however the TV isn’t capable of displaying UHD content, so it will scale it down to match your TV’s resolution. The same thing will happen if you watch movies using a 4K Blu-Ray player or play UHD games through your gaming consoles. Unless your device is connected to a UHD TV, the resolution will drop.
To get the best picture quality for streaming 4K content, you should opt for a 4K TV. Plus, many 4K TVs have 4K upscaling that take your Full HD 1080p content and render it closer to lifelike 4K, however Full HD TVs can be ample if you're after a smaller TV and you're only interested in 1080p content.