That makes slightly more sense.
The board has three oscillator options:
1. Do not fit OSC_CAN, C33, C34 or Y1. Fit the link - the oscillator can then run in RC mode.
2. Do not fit OSC_CAN or the link but do fit C33, C34 and Y1. The oscillator then runs in internal crystal (LP, XT or HS mode) at the crystal frequency.
3. Fit OSC_CAN but do not fit the link, C33, C34 and Y1. The oscillator then runs in external clock source mode.
So answering your question, OSC_CAN is four pin oscillator module. One that has the crystal inside it and produces a square wave output. You choose the frequency you want, they are available from a few KHz up to around 100MHz.
Brian.