Z Seam
When you print something it slices the object up into layers. Each layer has a start and stop. This looks different than the rest of the line that makes up the layer. This will always be visible. You can not make it go away. You might get it to look better by having your printer get better at start/stop of lines.
There are options for where the slicer will put the seam.
Random will put the start/stop at random places. You get little zits at random places on the model.
You can put the seam in the back. The back how you look at the object in the slicer. Hopefully you will not see it when the thing is sitting on the shelf.
You can put the seam along a corner. It is less noticeable there and you may not see it. A round thing obviously doesn’t have a corner. As it moves up the model it may pick a different corner at different heights.
For ultimate control you can paint on where you want the seam to be.
Vase Mode
In vase mode you get a single wall that goes up in a spiral and there are no seams. The bottom will not be vase mode and will have a seam. The object must have a surface you can draw in a spiral without stopping. If you can not draw the thing with a single spiral the slicer probably will not let you slice in vase mode. You only get a single wall, if you need the strength of multiple walls, this is not for you. People often use a bigger nozzle so the single wall can be a little wider for additional strength.