Activate this option if you want the 3ds Max FBX Plug-in to create tangents and binormals data from UV and Normal information of meshes. This way you have a tangent space representation of your meshes that you can use for advanced rendering.
Exporting tangent and binormal data is useful when you need to define the local coordinate system for each vertex in the mesh, which is referred to as “Tangent space”. This is often required for advanced rendering techniques such as normal mapping.
The 3ds Max FBX Plug-in reads the UV data and uses it to calculate the Tangent space data for normal perturbation in per-pixel lighting.