Is "ground information" a synonym for "terrain" in OBM?

Yes, one can import terrain in OBM.  Please see wiki for details:  Import DTM - LARS | LEAP | OpenBridge | OpenTunnel | RM Wiki - LARS | LEAP | OpenBridge | OpenTunnel | RM - Bentley Communities

Sorry. I'm referring to a Bentley document that says to "import ground information from another software via DXF." I asking which tool Bentley is referring to.  There's no context, or I could assume what they mean. Also, Bentley uses the term "terrain" to refer to a 3D-triangular-surface model. Ground information could be that, a DTM, TIN, or who knows what. I don't think you can import "ground information" with the Civil pane in OBM. You can import an alignment or profile, but not a "DTM" with the Civil pane. 

As mentioned above we have the Import DTM option available from Home tab > Bridge Setup ribbon group.  We also have addition tools available from the Civil Tab under Terrain Model.  You can find more information about the available option in this group by clicking on the link below.  

Terrain Model (bentley.com)

All the tools available in Terrail Model group are OpenRoads Civil tools - for help with use of these tools please see wiki page: Terrain Modeling - OpenRoads | OpenSite Wiki - OpenRoads | OpenSite - Bentley Communities

Please give me details about which document are you referring above about import ground information.

This statement is from accreditation@bentley.com : "Ground information coming from another software could be imported [into OMB] via DXF." There is no option to import DXF files in OBM's "Import Terrain." I don't know what Bentley means by "ground information." I'll ask "accreditation" what they mean. Thanks.

Yes, one can import ground information from a file (DGN, DXF) using the graphical filters.  This can be done using the Create Terrain from Graphical Filters tool under Terrain Model group.  See:  Video: Create Terrain From Graphical Filter - OpenRoads | OpenSite Wiki - OpenRoads | OpenSite - Bentley Communities