Can someone please explain to me what rebirth is and what all the hype is about?

Hello everyone I have been reading my first comic for about a week now (flash by goeff johns book one) and I am having an awesome time! So as I look to get into more and more comics this rebirth stuff seems kinda cool, if someone can explain it to me and let me know if I should get into it or wait until I read more comics. Thanks in advance!