Answers:
It is call cartilage. It act approaching a shock absorber so your spine doesn't rub bone on bone which would be extremely raw.
It is not "a tissue" but probubly the tissue. Tissue is inside of your body, it is around your bones etc.., therefor it is around your intervertebral disc.
http://en.wikipedia.org/wiki/interverteb...
http://www.madsci.org/cgi-bin/cgiwrap/~l...
It is the fatty stuff beneath the skin
Cartilage is a bit diff. than tissue, near is tissue and cartilage