Networking is about transmission of data from A-B within a network of connected nodes. Either you have a full meshed network which connects each node directly with each other (a lot of links),
or you could have a star network with a central hub (centralized), or you could do it like it is done today with the Internet, meshed networks where dozens of providers link with some of the others but not all, and a protocol tries to find the most efficient way to get from A to B
A decentralized company, is a company that is run in software and has the business propositions be implemented in code (including profits)
However, it does not necessarily need to be decentralized, it could be run on your own servers as well, BUT it CAN be decentralized like in BitShares