My question is, why is there 4 pins? Is this crystal somehow intnegrated with capacitors or what? But even integrated crystal with capacitors would have GND, OSC1, OSC2 pins - that's 3 pins and not 4....
No specific reason, no capacitors. It's an industry standard package, used both for oscillators (4 terminals) and crystals (2 signal + 2 ground terminals). You can review datasheets from major manufacturers, e.g. Abracon.
You are talking about crystal oscillator in contrast to simple crystal. Unfortunately the difference can't be determined by looking at the case, you need to check the type specification.