Basically they are electrons streaming away from the negatively charged (and usually heated) cathode and attracted by the positive anode electrode because they are negatively charged themselves. In their most common use, a cathode ray tube in an old fashioned TV or computer monitor, oscilloscope, and other visual displays, the anode is arranged so they pass down the tube to the screen which is coated with be material that glows when electrons hit it.
They were discovered and their properties investigated in early experiments with high voltage discharges in partially evacuated glass vessels by William Crookes and others in the second half of the nineteenth century.
Basically they are electrons streaming away from the negatively charged (and usually heated) cathode and attracted by the positive anode electrode because they are negatively charged themselves. In their most common use, a cathode ray tube in an old fashioned TV or computer monitor, oscilloscope, and other visual displays, the anode is arranged so they pass down the tube to the screen which is coated with be material that glows when electrons hit it.
They were discovered and their properties investigated in early experiments with high voltage discharges in partially evacuated glass vessels by William Crookes and others in the second half of the nineteenth century.
https://en.m.wikipedia.org/wiki/Crookes_tube