What do E, EW, and EI classifications mean?

These are European classifications: E (Integrity) means the glass prevents the passage of flames and hot gases. EW (Integrity & Radiation) means it prevents flames/hot gases and significantly reduces radiant heat. EI (Integrity & Insulation) means it prevents flames/hot gases and limits temperature rise on the unexposed side.

More questions

EI-rated glass provides a significantly higher level of safety than E-rated glass because it not only blocks flames and smoke but also limits dangerous heat transfer, protecting occupants and preventing secondary fires.
Fire rated glass(which is often referred to as fire-resistant glass,fire protection glass,anti fire glass or fireproof glass) is a specialized glazing product designed to act as a barrier against fire, smoke, and heat transfer for a specified period, helping to contain a fire and allow safe evacuation.
Yes, modern fire rated glass, especially EI-rated products, can remain transparent under normal conditions, allowing for natural light and visual connectivity while providing fire protection.