As a high level deinition a confidence interval is a range around a statistical parameter of a sample where you expect a percentage of the sample to fall within.
It is more complex then just this alone. It can be used to do many things, one of which is testing significance.
thanX Mr fantastic, here is the part of my lec note that I couldnt understand:
"The Gaussian distribution has the following interesting properties: approximately 68%
of values fall within 1 standard deviation (SD) from ; 95% fall within 2 SD; and 99.7%
fall within 3 SD."