What is a Pulsar???

Well.. I accept very recently i came to know that there is another definition for Pulsar...(Not the Bajaj Bikes that turn when Nurses with Short Skirt walk past)... This is a Pulsating Radio Star.. a celestial radio source emmiting Brief and extremely regular pulses of electromagnetic radiation. Each Pulse lasts a few Hundreths of a second(less than a nano) and the period between pulses is less than a second.... this info would do on this note coz the deeper i go , the harder its for me to understand.. now i learnt that there is one more pulsar apart from the ones that zip in the streets....