Maya is essentially a network of nodes, each with their own attributes, all connected to each other.
Yeah, I know, that's not really helpful.
So how I think of that, is a node is a virtual box that contains a bunch of information. The type of information determines exactly what type of node it is, and the exact values of the information determine exactly how that node behaves (or looks).

So a shader node will have types of information relating to color, how shiny, how reflective etc.
Polygon geometry generally consists of two types of nodes connected together, a shape node and a transform node. The shape node will tell maya (and you) what that geo looks like, is it square, round, how smooth is it. The transform node will say where that geo is and how it is oriented, pretty much the translate, scale, and rotate information (along with some other stuff).

So how do you see all this information? The attribute editor of course. All the different tabs for any object are all the nodes that are connected together. A shape node, a transform node, a material (e.g. lambert1), maybe some other nodes too. How do you see how these nodes are all connected? The hypergraph. Open it up and choose graph selected. You'll see how these nodes are connected, because the connections are directional, and they also connect via the attributes themselves. But I think that's enough for now. I hope that helps you out. I think it's important to understand how maya really works at the base level in order to do lots of troubleshooting and finding faster workflows.