Or “What is an ellipsoidal?” “What is a stage wash?”
There’s a lot of jargon in the audio visual world. A “leko” is a term used to refer to an ellipsoidal reflector spotlight. These are very common fixtures. They’re often used for a “stage wash”, or basic lighting of the presentation area.
Lekos can be focused and shuttered to hit specific areas, for example you might hear an AV professional talk about a “special” on the podium. Which is a slangy way to say “A light aimed just for that spot”. Lekos are also the fixtures used for gobos.
Unlike LED lights, lekos draw a lot of power and get hot. For that reason you don’t want to have one in a place where participants might brush against it, or leave articles of clothing resting on it (for example at a gala where attendees have long dresses).
If you have more than a few fixtures you’ll likely need additional power from the venue. In most hotels and conference centers this incurs an additional cost.
When do you need a leko? Obviously if the space isn’t bright enough. But also if you will be doing anything with a video camera, either recording or IMAG you almost always need additional lighting.