Bones, yes. Needed for animation, your mesh is weighted to them.
I don’t know which mesh you are working on and/or where it came from but if you plan to import any mesh into ME3 it will need to be weighted to an appropriate boneset. AKA say you import a mesh from a different game into 3ds and want to get that one into ME3 for femshep, then you can delete the original bones that came with the mesh but will need to import bones from a (similar) femshep mesh and reweight your mesh to it before you export.
If you exported a mesh straight out of me3explorer (or via umodel) and are making small adjustments in 3ds to reimport it later, you can most likely keep the bones the mesh was weighted to. Just make sure you check the weights on import into 3ds. The transitions should look smooth, if the weight edges are jagged, you might want to try to reimport or use an alternate actorX import script because this can cause weird things to happen when your mesh animates ingame.