What is the difference between alfa and bata?

do you mean alpha and beta? If so, this can be used in a number of ways. For example alpha testing and beta testing. Or first stage, and second stage. Something in alpha stage is probably an early prototype and so may have many problems. Once these are sorted it may become a beta prototype. At this point it will probably be more reliable... but is still not a final production version for release. You often hear these terms in software development.