Hi, Alexander!  Recently you wrote in a message to All:   
      
   ak>  "It is" and "this is" --   
   ak>  is there any difference or   
   ak>  both mean the same?   
        |(colloquial) do they both mean the same thing?   
        |(formal) do both have the same meaning?   
      
      
              The meaning is similar enough that if the best I can come up with   
   on short notice is a few examples, I hope you won't read it as a "rule"...   
   [grin].   
      
      
      
   ak>  For instance:   
   ak>  This is our plan.   
      
      
              We use "this is" & "here is" in reference to a concrete object   
   which is close at hand... e.g. "This is/here is the file you were asking   
   about, Sir."   
      
      
              We use the same construction in reference to an abstract idea   
   and/or series of ideas before explaining further.  A hockey coach might say,   
   e.g.,   
      
        This is/here is the plan [with or without diagrams]:   
        1)  Somebody gets the puck into the corner on the goalie's left.   
        2)  Kevin goes after the puck & passes it to Ryan, who is closer   
            to the middle but still on the goalie's left.   
        3)  Ryan fakes a shot... then immediately passes the puck to Alan,   
            who has been hanging around close to the other side of the net.   
        4)  Alan sneaks the puck through the opening on the goalie's right.   
      
      
      
   ak>  It is our plan.   
      
      
              It was my intention to answer this message more promptly....  ;-)   
      
      
      
   ak>  May there are situations when it is important when we   
   ak>  use "it" and when we use "this"?   
      
      
              Maybe other native speakers can help us out here.   
      
      
              In many situations it doesn't particularly matter which we use.    
   But you & I both use "it" in sentences such as:   
      
        Is it important to know when/where to use [blah blah]?   
        It's significant that [this author is a cell biologist].   
      
      
              We also use "it" in idiomatic expressions pertaining to the   
   weather, and sometimes to climatic conditions indoors:   
      
        It was [sunny/cloudy/windy] yesterday.   
        It's raining in Vancouver & snowing further inland.   
        It feels cold in the bedroom this evening.   
      
      
              OTOH, teachers in the primary grades used to hang signs all over   
   the classroom using full sentences such as "This is the door."  I gather they   
   don't place so much emphasis on complete sentences nowadays.  But whether a   
   sign says "This is the door" or simply "door" it's attached to a physical   
   object.   
      
              Hm.  Now that I've geared down from adult to primary/preschool   
   level another variation on the use of "this" comes to mind, i.e. a children's   
   song in which "This is the way we wash our hands" is accompanied by the   
   action....  :-)   
      
      
      
      
   --- timEd/386 1.10.y2k+   
    * Origin: Wits' End, Vancouver CANADA (1:153/716)