how do 2.4 Ghz transmitters work

how do devices like xbee's have clock signals to transmit at 2.4 Ghz do they have some type of crystal oscillator? Or is it something different entirely?

The bits are not sent as simple 1s and 0s. Data gets encoded so that the data is sent with a clock embedded in it. The receiver decodes the data as it comes in, recovers the clock, and determines the original data.

While not specific to 2.4GHz Wireless controllers, look at 8B/10B.

This is how serial protocols like SATA, PCIe, and HDMI work. 8-bit data is encoded as 10-bit symbols. This prevents a long run of 0s or 1s from ever occurring, so that the receiver's "clock recovery (aka PLL)" sees an edge often enough to reconstruct the transmitter's clock.

Wireless is a bit more complicated because the symbols get modulated in a variety of ways, but the concept is still the same: encode the clock in with the data.

Not sure I fully understand your question, but this is how the 2.4 Ghz frequency is generated.
The 2.4 Ghz transmitter frequency is generated by a voltage controlled oscillator which feeds
a very hi frequency divider called a dual modulus prescaler.
This chip divides the 2.4 Ghz signal down to a much lower value where its compared with a similar value from a conventional crystal oscillator using a phase detector.
The phase detector produces a variable output DC voltage which controls the frequency of the 2.4 Ghz oscillator.
This gives a stable frequency at 2.4 Ghz which equals the stability of the crystal oscillator used to do the comparison.

arduinoPi:
how do devices like xbee's have clock signals to transmit at 2.4 Ghz do they have some type of crystal oscillator? Or is it something different entirely?

On the face of it you are asking for a complete rundown of radio transmission technology,
and I haven't the time for that here!

All radio transmitters/receivers have an oscillator, almost always crystal or
SAW-filter stabilized (accurate frequency is vital), but the kind of device you
are talking about is a transceiver-on-a-chip - a complete radio transmitter and
receiver and a packet generation/reception section. The XBee has built-in
network protocol stack too (its basically a microcontroller as well).

The basic form of a transceiver is local oscillator, frequency multiply or shifting stages
(often incorporating PLLs, so the LO frequency can be derived from a single reference
oscillator, normally quartz), mixers/modulators, an IF-strip, an RF power amp, antenna
matching network... Wikipedia some of those terms perhaps!