Pre-conditioning is all about preparing the battery to accept recharging efficiently. From a user perspective, the quicker the rate of charge, the less time taken to reach a higher state of charge (SoC).
The rate, or speed, of the charge is affected principally by the current battery temperature, the SoC at the start of charge, the chemistry of the battery and its ability to accept a slow or fast charge (this is also impacted by the size of the battery - a larger capacity battery can charge faster than a smaller batter) and the capability of the charger (speed of charge in kWh).
Each car has a battery management system (BMS) that balances the ability to charge as fast as possible with protecting the battery from a charge speed that could damage it. This BMS factors in the variables mentioned above: battery temperature etc.
Tesla has a feature of preconditioning. In effect, the BMS works out when to warm or cool the battery enroute to a charge to bring it to the optimum temperature to achieve the fastest charge rate without damaging the battery. This preconditioning cannot be activated by the driver directly, rather the car does it automatically. Based on selecting a Supercharger (SuC) as a destination or where the car directs the driver to a SuC as part of a longer route. Earlier this year Tesla rolled out an enhancement where preconditioning would also be used for third party rapid chargers. These can be seen by pressing the lightening bolt symbol in the bottom left of the screen and selecting the three bolt list. Unfortunately, in the UK the list is not yet populated with any non-Tesla rapid chargers.
In conclusion, the car will precondition when it thinks it is appropriate and achieve a quicker charge at a SuC. But perhaps just regard it as a nice to have rather than absolutely essential.
