From what it looks like the valve is a solenoid actuated diaphram on-off full port valve. The following link shows the diaphram in a manually operated valve:
As can be seen in the diagram in the attached data sheet when the diaphram is in the full up position the flow path is full flow through the valve. The manual operator pushes the diaphragm "compressor" down over the ports to close the valve.
In an automatic solenoid actuated valve the compressor of the manual operator is replace with the upstream pressure that closes the valve diaphram against the openings of the upstream and downstream ports. This is due to upstream pressure forcing the diaphram down. Although the upstream pressure is just equalized with the upstream piping side of the valve, the upstream pressure applied to the diaphram is greater than the downstream piping side so there is a net force pushing the diaphram down over the outlet port and valve remains closed.
The valve closes by closing the solenoid valve so that the upstream pressure cannot bleed into the downstream side and is applied to the top of the diaphram. To open the valve the solenoid valve opens to allow flow from upstream to downstream side to bleed of the diaphragm. although still exposed to upstream pressure there enough pressure drop in tubing such that there is not enough force to close the diaphram.
The valve is used to provide a large diameter full flow solenoid operated valve by using the solenoid valve indirectly to operate the diaphram valve since solenoids connected directly to valves are usually low flow and small diameter solenoid valves.
The reference to 1 and 1.5 bar refers to the two maximum allowable minimum inlet pressure ranges of the valves as noted in the tables.
I believe the 2/2 way refers to the fact that the valve is 2-way (not 3-way) and can flow in both directions. Normally closed I believe indicates that when solenoid valve is de-energized the solenoid valve port is spring loaded closed to keep full inlet pressure on top of diaphram with port to outlet sice of solenoid valve closed. When solenoid is energized the port of the solenoid valve opens against the spring to allow flow in control tubing from upstream to downstream to bleed of the diaphragm.