Oscillator options like INTRC and INTRC clockout are described in the PICs Datasheet as it is a function of the individual PICs hardware. If it's in the Datasheet, don't expect to find it in the PICBasic documentation which is where a lot of people seem to take issue with this.

The DEFINE OSC setting is for the frequency your PIC is going to be executing at... eg 10MHz Xtal with PLLx4 means you're running your program at 40MHz and that is what PICBasic needs to know. So in that example it's DEFINE OSC 40.