What kinds of LEDs (chips) are there?

SMD (Surface Mounted Device): The LED is soldered directly to the PCB. The advantage over traditional wired LED lies in better heat dissipation and less space.

COB (Chip on Board): The LED is applied directly to the substrate, thus an "onboard" solution. The advantage is even higher packing density and a more homogeneous light output compared with SMD chips, since the individual points of light are almost not visible.