When you dig, you scoop or shovel up dirt, sand, or some other material. Your dog might whine to go outside so she can dig a hole in your dad's garden.
You can dig with your hands, a shovel, or even a tractor or backhoe. City crews dig up roads to repair water pipes, and gardeners dig small for planting bulbs. You can even say you dig your brother in the side when you jab him there. If someone says, "I dig you," they mean, "I understand," and if they say, "I dig your outfit," they like it. Both slang usages come from 1930s African American English.