i can try to explain the nodes and OSM.
OSM is in a sense only a huge dB with points/nodes/places on earth and the exact place is determined by satellite. You see your position on earth via this grid.by geospatial coordinates. This is the world wide grid that covers the earth, and gps machines like your mobile or smartwatch can register your position in any point in time.
To make maps in the internet via this dB of points/nodes, you tag these points and make relations between them.
If i position a point on the grid where in real life for instance there is a tree, i can tag this gps point in OSM as a tree. Each map renderer can now mak e a map and make a symbol of a tree on the pouint s that are positioned and tagged as tree, and so on for anything renderable.
The green dot visualising a tree in he ODM standard rendering
The same tree on sattelite and the point drawn and tagged.
When you say a point has a relation with another point, a line between these points is created. This line can also be tagged. This can be a lot of things, for this site the most important tagging is of course all kind of streets.
here is a street in edit mode, it has 9 nodes, the endnodes are grey, meaning there is a connection to another relation, another street on the right, and a track on the left side. The street is tagged as such and has a streetname.
To come to the point of your question: CS imports a bunch of points called nodes, filtered by the tags on a relation between points. The filtering of course is on all kind of streets. @JamesChevalier can elaborate on the details of the filtering.
There is a lot of info found ion the web, i can only encourage people to help maintain the OSM dB to give a good presentation of the world, free to use by everybody. It makes initiatives as CS possible.