Transforming objects into paths
In Inkscape, any shape, text, or object that you created can be converted to a shape. Don't be fooled when it doesn't look like anything has happened because any capabilities that you had before (dragging corner nodes to scale larger, editing text, rounding corners on a square) can be lost, but now, you would be able to edit the object's nodes just like any other path (such as in our previous example).
Stroke to paths
You can convert the outline or stroke of any object and convert that to a path. Select an object with a stroke set—then from the main menu, select Path | Stroke to Path.
Again, the overall appearance on the canvas does not change, but how you can manipulate the object. Take a look at the number of nodes before this spiro was converted into a path, versus after:
