Vias are also called metallization holes. In the double-sided and multi-layer boards, in order to connect the printed wires between the layers, a common hole, that is, a via hole, is drilled at the intersection of the wires that need to be connected on each layer. The parameters of the via hole mainly include the outer diameter of the hole and the size of the drill hole. When you need to draw a double-layer board or a multi-layer board, you can place the via hole to make the top layer and the bottom layer conduct.
Place two vias on the trace, then you can switch the trace between the two vias to another layer, or remove it.
During the routing process, use the shortcut key to change layers to automatically add vias. Shortcut V.
Note: The default cover oil for system vias