But why is there IR if it's a green laser?

Because, as previously mentioned, green DPSS lasers are built using an IR diode and crystals to convert it to green light, thus approximately 80% of the energy is absorbed by the crystals (poor quality ones absorb even more). As you might already know, no material is perfect and in consequence, some of the IR light goes through the crystals and is "fired" with the green light you see at the end of the laser. Despite the fact that you can't see IR doesn't mean you can't get hurt by it. Again, use safety glasses!