Summary: A joint report released this week by the National Council for Voluntary Organisations and the Charities Aid Foundation (you can read it here) showed that charitable giving in 2011/12 was lower than at any other point in the last eight years, adjusted for inflation.
What does the chart show? The organisations that produced the report carried out a survey with the help of the Office for National Statistics, asking people if they gave to charity and if so, how much. From this data they have estimated the total amount, in billions of pounds, given to charitable causes by individuals in the UK. This data has then been adjusted to take inflation into account. Although the numbers used are estimates, they are "the most accurate available estimates of the total amount donated to charity" according to the two organisations that produced the report.
Why is the chart interesting? After a period of steady growth, there was a big drop in giving between 2007/08 and 2008/09, which coincides with the financial crisis, but then donations appeared to recover somewhat. However, giving in 2011/12 is estimated to be lower than in any of the previous eight years. If accurate, this decline in total giving is an interesting indication of a change in individuals' priorities, presumably as a result of the latest period of recession and people's perception of the outlook for the UK economy.