Strobing is an effect that occurs when narrow stripes appear on video, in which the stripes flicker. The main culprit is neckties, as they tend to have small stripes at a diagonal angle, but striped shirts or other striped objects can also cause it (for instance, tennis matches can have flickering white lines). Strobing mainly occurs on live TV with guests; experienced TV people tend to avoid clothing that will cause it.
As this is essentially a visual artifact of Ludicrous Precision, higher definition video, such as Digital TV and HDTV, actually tends to make it worse. Counterintuitively, video can sometimes actually improve in quality if it is slightly blurred.
In analogue systems, the shimmering effect is caused by the colour being carried over the same signal as the luminance using a subcarrier. Stripes cause a high frequency luminance pattern when the television mistakes for the colour subcarrier.
Strobing can also occur in Video Games, mostly those in polygonal 3D. Objects such as power lines can appear to be made of floating segments, and thin fence posts can appear to flicker in and out of existence. Unlike live-action examples, the objects line up exactly with the pixel raster, creating pixel-perfect jagged edges. However, most modern video games have ways to reduce or eliminate this effect, such as anti-aliasing to smooth out jagged edges around objects. Starting in The New '20s, PC game upscaling algorithms like Nvidia's DLSS use data from previous frames to prevent thin objects from strobing.
Closely related to the concept of Moiré patterns. Also compare Raster Vision. Has little relation to Epileptic Flashing Lights.