Core concepts

Via

A plated hole that connects copper on one layer to copper on another.glossary, Core concepts

A plated hole carrying a track from one layer to another; costs space and a hole in the ground plane.glossary, Physical / electrical concepts

How it looks

Real image: CORE3588, rendered by KiCad from our board file

Top side, a 5 x 3.6 mm patch near the power-switch chip (U1). Each via is 0.6 mm across. CORE3588 has 508 of them.

1A via on the ground net: the grey ring is its copper pad, the dark dot in the middle is the drilled hole (0.3 mm).
2Another via, this one carrying the READY light signal down to the bottom layer.

Real image: CORE3588, rendered by KiCad from our board file

Bottom side, the same patch seen from below (left and right are swapped, like looking at the back of a page).

A via joins tracks on different layers. On CORE3588 every via goes all the way through (a plated through hole); its position and size end up in the drill file.

Each via cuts a small hole in the ground plane; too many in a row can block the return path of a differential pair.