Vector and raster floorplans
A vector drawing stores lines as coordinates: a wall is two points and a thickness. A raster drawing stores a grid of pixels: a wall is a run of dark dots that happens to look like a wall. Both arrive as PDFs, and they are not the same document.
The quickest test is to zoom in. Vector lines stay crisp at any magnification, because they are redrawn at each zoom level from their coordinates. Raster lines go soft and then blocky, because there is nothing underneath the pixels to redraw from. Selectable text is the second tell: if the room labels can be highlighted, the sheet is vector.
How each one comes to exist
A vector sheet is what a drawing package exports directly. A raster sheet is what happens afterwards: a print that got scanned, a scan that got emailed, a photograph of a print taken on a site visit, a screenshot pasted into a slide. Older buildings arrive this way as a matter of course, and so do plenty of new ones, because the marketing copy of a drawing has usually been through a flattening step somewhere.
Why it matters
Measurement is the difference. On a vector sheet, a wall has a stated thickness and a stated length in the file, and the title block states the scale that converts them into metres. On a raster sheet none of that survives: what remains is an image, and any dimension taken off it is an inference from pixel distances against a reference of some kind.
How StudiO treats them
Both are accepted, and they are handled differently on purpose. From a vector PDF, StudiO takes the scale from the title block. From a raster image, it produces an explicit scale estimate and says that the number is an estimate, so anyone reviewing the model knows which kind of sheet it came from. Wall segments are then measured and typed the same way in both cases.
For a great many buildings, a scan is the only input there is.