Ever since the United Nations Framework Convention on Climate Change was created in 1992, there has been a division between rich industrialized countries and poorer industrializing countries. The rich countries have typically been the strongest proponents of climate action, arguing that with all this new climate science it's everyone's responsibility to cut back on emissions. In response the poor countries point out that rich countries got to reap the rewards of fossil-fuel driven industrial growth, and that growth is largely responsible for the GHGs trapped in the atmosphere.
The COP 21 negotiations are showing that both groups have succeeded in making their point, to some extent. That each country has shown up and pledged to reduce their emissions, including developing country giants like China, India, and Brazil, means the developed countries have succeeded in making emissions reductions a near obligation. On the other hand, the developing countries have hinged the success of the Paris Agreement on the strength of the text's "loss and damages" provisions. Essentially, in exchange for reducing emissions, developing countries want financial assistance from developed countries to help them cope with climate impacts.
It's a reasonable request, and one the developed countries have essentially already agreed to in a broad sense, but it raises a number of thorny particulars that negotiators are having trouble resolving. Resolving questions like Who has to pay, and how often? and Who gets to receive, and for what purpose? are one challenge, but a potentially bigger hurdle will be the conceptualization of "loss and damage" provisions. Developed countries are categorically against any language in the text suggesting they have legal liability for climate damages like loss of land, building damage, etc. They are willing to make voluntary financial payments, but won't accept legal responsibility for climate impacts:
Industrialised countries acknowledge that they are obligated to provide climate finance, but with an eye on the changing global realities, would like developing countries "in a position to do so" to contribute to the money pot. This attempt to increase the donor base has been strongly contested by the developing countries.
The other contentious issue is who is eligible to receive the funds. All developing countries are eligible but increasingly there is talk of funding for "vulnerable" countries. There is however no clarity on what defines vulnerability. Many in the negotiations see this talk of vulnerable countries as a bid to divide up the developing countries bloc. The G-77 and China comprising a diverse developing countries have presented a resolutely unified front on the question of finance.
Ultimately the developing countries may realize that no country is going to accept the legal implications of a robust "loss and damages" provision. Instead, they might end up angling for a strong financial commitment. Rich countries, for their part, can make those commitments without implicating any legal obligations. Instead of providing compensation for damages incurred from climate hazards like hurricanes, they can subsidize hazard insurance for countries in particularly vulnerable areas. Many are saying the "loss and damage" provisions will come down to the wire. Stay tuned.