As mentioned in our introduction, MLA stands for Micro Lens Array. This technology is a hardware-based change that LG have introduced, starting with the G3. The G4 now implements it for all models aside from the largest 97" size. Thanks to a thin layer of microscopic lenses on the OLED panel, more light can be bounced and redirected towards the viewer to achieve improved luminance.
The G1 does use the brand's OLED evo panel to make it brighter than the generation that came before it, and indeed the mid-range C1, but MLA takes it to a new level. For example, compared to the regular OLED panel on the entry-level B4, the second-gen MLA is up to 150% brighter according to the LG store page.