Tactics

Can i create tactics like pins, skewers, double attack, discovered, etc., or it naturally occurs in a game and we want to find it? Pls anyone

Both.

Create a fork:

Naturally occurs:

I think you are asking if you can intentionally create positions with winning combinations. The answer is no: those arise naturally only sometimes when your opponent makes enough mistakes, and even then you might just win by material rather than by a showy combination. And obviously you can create pins.

Pins fall into a different category of tactics than skewers and forks, since players create pins all the time as a matter of course in standard openings, without harm. Pins are not "forcing moves" for one thing: most of those dazzling sacrifices you see in combinations are forcing moves that fall into a different category that I call non-positional "editor" moves, but that's a huge topic I'm still investigating myself. (http://www.chess.com/forum/view/general/list-of-tactics-from-palatnik-amp-alburt)

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(p. 4)
   Is there an infallible recipe
for such mates? We do not
think so. In the example we
have just given the King was
collected at its initial square
and gradually dragged to the
other side of board, where
it was mated.
   One thing can be said, how-
ever: An experienced player
feels instinctively that posi-
tions, such as the one in the
diagram, are full of latent pos-
sibilities. Since all the moves
are forced and since there are
no variations to complicate
(p. 5)
the line of play, it is relatively
easy, with some practice, to
forsee the consequences of
the sacrifice and to calculate
the number of moves neces-
sary to bring about the mate.
And even if he is not able to
foresee the whole mating proc-
ess, the good player will "feel"
that the King is about to em-
bark on a journey from which
it will not come back.

Renaud, Georges, and Victor Kahn. 1953. The Art of Checkmate. New York: Dover Publications, Inc.