I'm not asking how to bevel a shape's edge, I'm asking how to create something like this:
For this, I created a cylinder of default size and scooted it 1m on the Y axis so that it appears as if the cube as a rounded face. However, this leads to Z-fighting between the two separate objects. I would like to know how to alter the cube's face so that it is a single shape with a rounded face. Sorry I don't have the vocabulary to be more clear.
If you want that exact shape, just leave the cylinder where it is, but select all the faces that are inside the cube as well as the top and bottom, and delete them.
Next, if you added the cylinder in object mode, select the two objects and join them with Ctrl+J. If you added it in edit mode, then they're already one object so you're good to go. Then, back in edit mode, select the outer faces of the former cylinder and the edge of the cube. Press F to make a face. Do this for the top and bottom.
Then, just select the whole thing and pick Mesh > Clean Up > Merge By Distance to get rid of any extra vertices.
You may want to delete the inner face of the cube that is no longer visible as well.
