What is horoscope can someone explain it to me thorughly and what is this talk about the planets and the stars being allighned at the right ?

Thoroughly?  No.  Not in the space given here not to mention the time it would take to do that.  For example, would you demand someone explain chemistry to you, thoroughly, right here, right now?  Of course not.  Same is true for astrology.

Astrologers look at the positions of the planets (which, for their purposes, includes the Sun and Moon) and stars and their geometrical relationship to each other.  Those positions are, for reference, placed on a map of the sky for a particular moment as viewed from a particular place, and then based on the astrologer's knowledge of the subject interpreted. Very few, if any, astrologers believe the planets emit rays that affect us all.  If they do, they're in good company.  Aristotle believed that (or something like it), but for non-astrological reasons. 

Most common of all is natal astrology, which is the astrology of a particular human being, his fate and/or his personality. However there is also, mundane astrology or the astrology of nations, astro-meterology - the astrology of the weather, horary astrology, the art of answering questions using an astrological chart, and electional astrology, which is finding the right time to begin an endeavor.  Almost all human cultures have or had some kind of astrology as part of it.

There are tons of books that explain this in detail. The better ones require a background in the subject that you don't seem to have.  If you want more, you'll have to be more specific and accept a more limited answer.