What is the difference between variables and factors?

I'm not getting the use of words like factor and variable. Are they interchangeable?

Regarding Variable vs. Factor -- an easy distinction between the two is that the observed scores that we collect are considered "variables" whereas "factors" are those unobserved things that we use to represent underlying relatedness between these variables. In psychological settings factors often are taken to represent "constructs" or theoretical psychological traits that cannot be observed or directly measured. In factor analysis parlance, inter-subject differences in underlying "factors" manifest in differences in observed "variables".