Do jewelers mark their jewelry?

I've always wondered, do jewelers typically mark their jewelry with some sort of identifying signature or hallmark? It seems like a logical step to ensure authenticity and traceability, but I'm not entirely sure if this is standard practice across the industry. I've noticed some pieces have tiny engravings or stamps, but I'm curious if there's a universal standard or if it varies from jeweler to jeweler. Could you elaborate on the typical practices and protocols surrounding jewelry marking?