OLED and QLED panel types use the same basic component to create images on screen: a power source, a light source, and a color source. The key differences are exactly how these panels get power, light, and color.
A QLED screen, mostly seen in Samsung, TCL, and Hisense models, uses a modified LED panel and a "quantum dot" screen to create images. The "quantum" in QLED seems to be more of a catchy marketing term than an allusion to actual quantum tech, but it does give you enhanced color and detailing over a regular LED display.
An OLED panel, found in LG, Sony, and Vizio TVs, uses an array of mini LED lamps that are individually lit along with organic substrates for color. The individual LEDs allow for true blacks to create stunning contrast and make colors pop. It's an expensive technology to produce, so OLED TVs are pretty pricey. But if picture quality is your top priority, it's a worthwhile investment.