Items 1 ,3 , 6 are the same part ( except on our engines we ahve a chain not a belt ) This is a device that maintains proper tension / take the slack out of the timing chain.

2 , 5 are the same part, they vary the intake camshaft timing relative to the crankshaft. This gives a broader flatter power band ( Rather than the engine being tuned to make power at a specific RPM , the adjuster broadens the power curve. As a side note, many intake manifolds use a long / short runner flap valve to help stretch out the power curve as well. )

4 This is a non part though in some sense the electro magnet coil and cam adjuster could be considered a solenoid system but no one in the USA is going to refer to it as such. ( Unless it as an artifact from German / English translation. )