summary() reports the ppp-value of the test that the coefficient on (Intercept) is zero to to be < 2e-16. This scientific notation states that the ppp-value is smaller than 2101621016\frac{2}{10^{16}}, so a very small number. The reason for this is that computers cannot handle arbitrary small numbers. In fact, 2101621016\frac{2}{10^{16}} is the smallest possble number R can work with.