What is NIR LiDAR?

The simple answer is that lidar sensors coupled with NIR cameras can collect point cloud data that can then have the NIR values "embedded" with them, the same way RGB values can be assigned to point cloud data collected with high res photos.

LiDAR sensors are not "coupled" with NIR sensors. Most LiDAR devices are NIR sensors. A LiDAR works by emitting a LASER beam pulse in a single wavelength and measuring the travel time when the pulse returns to it. The receiving sensor can measure the intensity of one or several return for each pulse. Topographic LiDAR use wavelength in the NIR (most of the time 1550 or 1064 nm) for eye safety reasons. Bathymetric LiDAR use green (532 nm) in order to reduce absorption by water, but this can cause eye safety issues.

The intensity values are usually stored in the raw files as full waveform or for the main returns only. It is worth noting that the NIR value stored on a single return comes from a fraction of the emitted signal if the same pulse had several returns. Interpreting the intensity of multiple returns as a reflectance value of the observed surface is therefore tricky because the area of the surface contributing to this return is unknown.

Of course, it is possible to carry other sensors on the plane equipped with LiDAR (e.g. a multispectral sensor) in order to assign other spectral vules to the point cloud. But then you have more contraints on you flight (multispectral sensors are passive, so you can't use them during the night).