A car parked on the road e.g. outside your house, for a few days is probably not abandoned. It is worth checking to see if it is taxed, you can check if the car is taxed on the Gov.uk website.
If it is taxed and in good condition and parked on the public highway, it is unlikely to be abandoned.
A vehicle that isn’t taxed should be reported to the DVLA as should a vehicle which has a statutory off road notice (SORN) but remains on the public highway.
A vehicle that doesn’t look roadworthy may have been abandoned so you should report it to us.