I think the term your grasping for is geology nerd.
What's the diference between radio carbon years and astronimical years?
There is no difference, apart from radiocarbon years are counted backwards from a fixed point in time, the point in time is called BP (before present) which is 1950 to be precise, so a radiocarbon date of 6000 years is 6000 years before 1950 or 6000 BP.
How do they use carbon for dating purposes?
Radioactive carbon called carbon14 is produced in the atmosphere and absorbed into living organisms. The amount of carbon14 absorbed is relative to the amount of carbon14 in the atmosphere at the time the organism lived, itís roughly constant but calibration tables are used to improve dating. Once the organism dies the carbon14 starts to decay, the half-life of carbon14 is 5730 years, which is the time it would take for half the carbon14 to decay. To date organic material you simply need to measure the decay rate as it stands now and compare it with the known decay rate, which will tell you how much carbon14 is left and so how old the organic material is.
If I eat an apple and die and the apple decays at a rate of half the apples mass per a day the CSI team that investigate my death could ascertain that I died two days ago if a quarter of an apple was found in my stomach. Half the apple decayed on the first day then half of the half on the second.
The difference is that with carbon14 they measure the rate of decay by monitoring the decay particles that are emitted (about 15 per minute in atmospheric equilibrium) not the amount of non-decayed material.
Hope that helps
But don't tell anyone I told you