Yes, the two oscillators are different. The reference should be accurate and stable, so that the output from the PLL's VCO is also.
A simple use of a PLL is to provide a higher, accurate (as accurate as the reference) digital clock. They are often inside a chip like a microprocessor or FGPA. It allows a simpler, cheaper and, importantly, a lower EMI-producing external clock source.
That's a 'niche' use of them really though. They are widely used in radio communications. For example, a CB radio might have 80 channels, which need to be accurately generated. By using a PLL with a lower, accurate crystal clock source (reference), it can be multiplied up into each frequency/channel step required by changing the division ratio. Each frequency output step will be as accurate as the single reference. The alternative, without a PLL, is the old-fashioned way of using a continuously tuned oscillator (inaccurate, drifting, always needs adjusting) or a separate crystal for each required channel/frequency - that's not practical for lots of channels.