"Recommended for beginners" means: they are supplied already including everything needed for observing, they can be set up in a few minutes and the operating instructions are straightforward.
Among "Recommended for beginners" are also small optics or solar telescopes which can be used with a photographic tripod.
All telescopes with an aperture of 12 inches (305 millimetres) upwards are more suitable for advanced observers, as handling is more complex. In particular, the colour-true apochromatic refractors generally exceed a beginner’s needs.
The classification according to beginners, advanced and for observatories is for orientation and is not meant to rule out or exclude in any way.