Is 69ing an actual thing people do?

Okay so my boyfriend just suggested to try 69 and I have never given a blowjob or even remotely wanted to, but I also want to pleasure him and do things he wants to do. So is this something people actually do? What do I do? Also how do I give a blowjob? I know it sounds stupid but I’m nervous to even do it. My jaw does not open that much 😂