Can anyone explain me the difference between Factor Anaysis and PCA?
Principal components don't have to make sense, they are just artificial numbers, summarized data if you will, used e.g. for visualizations

With factor analysis you try to find a latent variable (an underlying mechanism) that explains the data. Factor analysis is often used in psychology, eg the personality trait extraversion (the factor) explains certain behaviours (eg certain behaviours reported in a questionnaire)