DXFs are primarily a 2D CAD file format. However, as we discussed previously, the DXF format is freely extendable due to it being written in ASCII and the fact that any application has a free license to develop on this format. Therefore there are scenarios in which you can find DXF files containing 3D model data.
If you intend to work with 3D models (as opposed to 2D drafting) we would recommend using a file format designed specifically for this requirement because 3D models are highly complex and DXF files which contain 3D data are often very rudimentary. Additionally, most applications which support DXF files do not read the 3D data contained within the DXF. Instead they assume the DXF is 2D and subsequently retain only the vectors on the X&Y axis.