How can a car battery be charged by dynamo (or is it an alternator?) at the same time it is being used by the car components?

In short, it can't. If the battery is being charged then current is flowing into it, so it can't be powering anything. It is the charger/dynamo/alternator that is powering the components whilst charging. In the case of a dynamo or alternator, if the output drops below the open-circuit terminal voltage of the battery, the battery takes over powering the components and is therefore no longer charging.

The battery is only being used when the alternator is not running. While the alternator is running (delivering power), the battery is essentially just another load like lights, radio, etc. For most of the time, the alternator is just maintaining the battery charge and thus supply little actual current into the battery.

The same way a laptop battery can be used and be charging. And if you have more current from your dynamo than is needed to power the lights, etc. those can be powered while charging the battery.