what is the Vertical and Horizontal distribution?

Vertical distribution : Distributed processing is equivalent to organizing a client-server application as a multitiered architecture . Place logically different components on different machines.
Horizontal distribution : Distribution of the clients and servers - more common in modern architecture. A client or server may be physically split up into logically equivalent parts, but each part is operating on its own share of the complete data set, thus balancing the load.

I tried to understand the difference between the vertical and horizontal. what's the meaning of "logically" and "physically" ?...but I can't! Does anybody know?

Solution

AFAIK

horizontal - You add more machines. These machines are equal meaning that they play similar role. For example you have Node server that handles all requests. You install it on three machines. All these machines do the same thing. When the load is high you add another machine with Node server.

vertical - You get better machines to handle the load. Also machines play different roles - for example you have Authentication server on one machine and Node server on the other.