Here's a breakdown:

* Cathode Ray Tubes: These are glass tubes with a vacuum inside. A high voltage is applied to the tube, causing electrons (which were called "cathode rays" at the time) to be emitted from the negative electrode (cathode) and travel towards the positive electrode (anode).

* Thomson's Experiment: By applying magnetic and electric fields to the cathode rays, Thomson was able to observe how they were deflected. This allowed him to:

* Determine the ratio of the electron's charge to its mass (e/m).

* Conclude that the rays were made of negatively charged particles, later identified as electrons.

* Suggest that atoms were not indivisible but contained smaller particles, which led to the "plum pudding model" of the atom.

So, the cathode ray tube was the key piece of equipment that allowed Thomson to make his groundbreaking discoveries about the nature of the atom.