Last night my dad told me that there is a way to plug a linux computer into a linux computer and it would become virtually one machine, the cpu, the memory, and all that would be shared between the two as if it were one computer, but he said he does not remember how, so I searched google, but found nothing, does anyone know anything about this and how to do it?
If only it were truly that simple!
This is not possible. You could use 2 machines networked together through ethernet or by creating your own LAN with a switch. The problem with this is the software you are using must support clustering of some kind.
That would be very cool, but distributed virtual memory, while workable in a research context, isn't too feasible in reality, although with really fast networks available these days, it is becoming less of a problem.
The only commercial or free OS I know that truly supports network computing, is QNX. It's a micro-kernel message passing OS with integrated networking where the network becomes the computer, more in truth than most other systems I've worked with (I have almost 30 years experience with it). It is commercial, but free for personal use. It is used to run nuclear power plants, Cisco's fault-tolerant series of routers, the manipulator arm on the space shuttle, etc. If you are interested in that, go to QNX Realtime operating system for more information.