Microcontroller Clock signal

I am bit confused with micro controller input clock signal. Should it be it a pulsed signal or sine wave? Generally the output of a crystal is sine wave which is given as input to micro controller, will the controller convert this wave into pulses and does the processing?

The oscillator circuit is usually shown in the datasheet.. The signal is indeed converted to a square wave, so any wave ie RC ( more triangular ) and XT / HS ( sinusoidal ) or buffered ( square ) will work okay..