I am not a hardware guy, but from my understanding a CRT uses an electron gun a distance from the screen to cause a matrix of phosphors to emit light. Hence the depth of CRTs. The electron gun can repeatedly scans from top to bottom, left to right (or whatever direction).
It can be adjusted to make any number of vertical "lines" as it sweeps over the phosphor matrix, but the matrix has a fixed dot-pitch. Because an electron beam is being shot at the matrix from a distance, there's a certain degree of bleed-over to neighboring phosphors. Firing electrons at the phosphors at coordinate 100,200 means a little bit of energy is also received by 99,199 and other neighboring "virtual pixels."
In other words, while the phosphor matrix was just as rigid as the pixel matrix of an LCD, the power source that caused light to be emitted was not perfectly matched 1:1 with the matrix. There isn't an electron gun for each pixel, there is a single electron gun for the whole display.
By comparison, each pixel in an LCD monitor (putting aside the three internal pixels for colors) is an individual mask over a uniformly white back-light. The panel adjusts the opacity of the mask to allow more or less of the white backlight through. The mask over a backlight is what gives LCDs a challenge with viewing angle (because there's a non-zero gap between the light source and the mask and the mask itself has a non-zero depth).
Finally, as I understand it, a plasma television is a bit like both. It's a matrix of phosphors like a CRT, but with individual power sources for each pixel like an LCD. Because light is emitted at the surface, plasmas tend to have very good viewing angles.
OLED then is, in my opinion at least, a spiritual successor to plasma. OLED emits light at its surface like an LCD or plasma, but uses no mask layer over a backlight, like a CRT or plasma.
(Take all of the above with a grain of salt because I'm just a layperson when it comes to hardware.)