Interpreting Auto correlation results

I used xcorr function to compute the autocorrelation of my input signal. I obtained a graph, which is shown below. How to interpret this? I read that autocorrelation helps in finding the patterns in the data. And i have went through some of the properties of the auto-correlation. But i am finding difficulty in obtaining information regarding how my input data is correlated with itself. Do i need to compute any other things in order to get this information?