I'm a nurse at a hospital.

DNR is do not resuscitate, so if you have a DNR, and the people around caring for you know you have a DNR, and no one from your family is trying to argue with the DNR, the they will not start CPR/BLS/ACLS (chest compressions, rescue breaths, intubation, defibrillation, meds, etc.) if you stop breathing or your heart stops beating.

A living will is a separate document and you do not need one to have the other, but they often go together as they are typically considered when someone is nearing end of life or has a quality of life compromising condition. A big reason for that, is the more sick or aged you are, the less likely a resucutation attempt will be successful.

Whether you want to be a DNR now or not, discussing your wishes for what kinds of medical care you want should you become unable to make decisions for yourself with your loved ones is a conversation you should have early and at regular intervals. You can make a living will with resources like the 5-wishes or other tools. Or you can designate a MDPOA to make those decisions for you.

Making sure you're family/chosen family knows what you want and making sure they will honor it is more important than any document. Families can and do override DNRs (thanks to a highly litigious healthcare system/country, I'm in the US). If you have documents, make sure your family knows where they are and make sure your primary care provider has them too.