To concur with LeeG's response, that does look like it was done by colouring the wood and then sanding through in some areas and not in others. Where the colour is removed most can be a little hard to control especially if the wood is not completely flat to begin with.
Even for a furniture piece I would strongly recommend applying a clear topcoat for protection. If used on a floor I think this is mandatory, otherwise the wood will begin to look grubby very quickly with even light foot traffic.
For a similar look with more control over the lighter and darker areas you can irregularly brush or wipe on on a coloured varnish or gel stain (gel stains are basically slightly thicker coloured varnish). You can do this directly on bare wood, or over wood that has been lightly sealed with thinned shellac or varnish, or with a commercial sanding sealer (which are often primarily thinned shellac or varnish). If you seal the wood the effect is slightly more controllable, as you will more easily be able to wipe colour away from areas of your choice.
Here also I would apply a clear finish for an overall protective coating.
Polyurethane varnish is a good choice for the topcoat. Oil-based poly tends to have a slightly yellow cast (quite possibly this was used on the project in the posted photo), the waterbase version goes on milky but dries completely clear. Use at least two full-strength coats.