Prototype printed circuit boards are quite complex, and each separate board is created with a specific purpose in mind. This can mean anything from having a board as small as one layered, to small batch pcb assembly made with numerous different layers.
The problem with all of these layers is that there is a lack of space for the engineers to work. This is where blind and buried vias come in as a means to save space but not compromise components.
Here is a beginner guide on these interesting techniques for pcb fabrication and assembly.
What is the difference between blind and buried vias?
A blind via is a copper hole that connects only one outer layer to one or more inner layered. These are only used to connect one component, and you are able to see the connection when it is on the board.