It's an abstraction.
Imagine an instruction that says to "draw a line starting at location A in direction B, make it C long and curve it D".
The actuality is a bit more complex / rich than this, but this is conceptually what it's about. You can see how vector instructions could be scaled or moved easily using math on the variables A, B, C, D...
Thank you exactly what I needed
Drafting applications like Autocad are all vector. Because the end locations and angles of lines, are stored as a highly accurate mathmatical value, errors are tiny compared to using a bitmap application like Photoshop. Although Photoshop does have vector capabilities.
Where as Photoshop is a bitmap application with vecot capabilities, Adobe Illustrator is the other way round. It means you can scale an object with no loss of quality. Like a Photoshop Type layer.