China DOS Union

The following questions are only about the situation under DOS.
1----Does the video buffer actually belong to part of the RAM on the motherboard, or part of the video memory on the graphics card that we talk about.

2---The motherboard ROM--BIOS has video driver code, so why is there also a graphics card BIOS chip on the graphics card? How are the two used.

3---Are the address spaces of the motherboard BIOS chip, the RAM stick, and the graphics card's video memory all in the same logical space? For example, if the BIOS chip has 1 MB of storage space numbered from 1 to 1 MB, then is the RAM's (64 MB) storage space connected after that 1 MB, and then the graphics card's video memory space connected after 65 MB. This question is really complicated. What I actually want to ask is how these three are addressed.

Actually I'm not too clear on it either, but my understanding is:
1, the video buffer is also on the graphics card, but it is generally copied to the lower part of memory for use.
2, the video driver and the graphics card BIOS are two different things, like the relationship between the system boot record and the FAT table, a calling and called relationship.
3, I think the space within 1M is for DOS, and 1M－64M is called by the HIMEM program.

Maybe the way I put it misled the poster above
Actually I only care about whether the contents of the graphics card's video memory and the contents of the motherboard RAM have a mapping relationship. If so, then does that mean as long as you modify this mapped part in the RAM, the video memory will be modified along with it.