ABS drain joint sealant and further questions

[Stolenbase]

I've recently purchased a 2000 325S and we decided to redo part of the inside. I pulled the toiled and tried to unscrew the flange. It turned, but it carried some fittings and pipe with it. A straight piece of ABS disconnected from the fitting downstream from it and I brought out an assembly that is about 18 inches long.

It was sealed with something less permanent than cement. It looks like tape (maybe even electrical tape) or putty.

I've searched and read, but I can't find what the substance would be. What do I put back on the pipe to seal it? Is the fitting downstream from it the grommet to the holding tank?

I have a picture of part of the assembly but didn't think to photograph the hole in the floor.