Amateur radios are in the usually low voltage devices, mostly designed for 12V, rarely for 24 or 48V. This means that in almost every case you need a power supply at the station. The power supply transforms the AC voltage of the supply network from 230V to 12 or more precisely 13.8V DC.
There are many criteria to consider when choosing a power supply. Fixed voltage power supplies (fixed to 13.8V) are safer, you cannot accidentally set the output voltage wrong. But you can't use them for experiments on devices with a different voltage. Power supplies with variable output voltage are more versatile, but you have to make sure that the correct voltage is always set.
Then there is the decision between classic transformer power supplies and switching power supplies. Switch mode power supplies are wrongly said to cause interference on short wave or VHF. In principle this is conceivable, but can be effectively avoided by careful circuit design and shielding. Switching power supplies have the big advantage that they are smaller, lighter and more efficient than transformer power supplies. It is also important to ensure correct power factor correction (PFC) for switching power supplies. Without this, a switched-mode power supply would not be permitted in the EU.
The power of a station power supply - no matter what type - should not be too low. Even if the transceiver only needs 22A at peak load, additional loads are quickly added. In general it is advisable not to operate a power supply at the 100% load limit. A healthy oversizing ensures cool operation and a very long life of the central power supply.