Is Apple MacBook Pro compatible with the LG LED PG60g projector?
If your MacBook Pro has a HDMI connection, you just need an HDMI cable. (The current MacBook Pro's have built in HDMI.)

If you don't have built in HDMI You need a Mini DisplayPort to HDMI Adapter and a HDMI cable. (If you have a ThunderBolt port, this can be used as a Mini DisplayPort connection)

You could could also us a Mini DisplayPort to VGA Adapter. This will work for most applications and presentations. However, VGA will run into issues with rights managed video. DVD's, iTunes and many other video streaming services will not be allowed to display on a VGA connection.

If you actually have the new MacBook (non-Pro) with the USB-C connector, you will need a USB-C to HDMI adapter.