Most chargers have long relied on silicon to convert mains electricity into the low voltage a device needs. Gallium nitride, a material that handles power with less wasted heat, lets the same job be done by a much smaller and lighter charger, and its use has spread widely for phones and laptops.
The practical benefit is a single compact charger that can power several devices and travel easily. Because less energy is lost as heat, these chargers also run cooler. The trade-off has been cost, but as production has scaled the price gap has narrowed, making the smaller design increasingly common in the box or as an upgrade.