whats the difference between class interval, class size,class limit,class mark and also ranges,width and length of rectangle ?

Answer:
              Consider following frequency distribution.
         
Class interval :    The difference between upper and lower limit of class is known as class interval.

Example :          200 - 299 is a class interval

Class size :       class size is the difference of upper and lower limit of our class.
 
Example  :        class size = 299 - 200 
                                     =  99 ( class size for interval 200 - 299)

Class limit :       Class limit is the smallest and largest observation in the class.
Example :         For 200 -299
                        lower class limit = 200
                        upper class limit = 299

Class mark :      we can calculate class mark by formula 
                     $class mark = \frac{upper limit + lower limit}{2}$
Example     :   class mark for interval (200 - 299) =  $\frac{299 +200}{2}$ = 249.5

Width of rectangle :  width of the rectangle is directly proportional to the class interval
Example :                 Width of rectangle =  for (200-299) = 299 - 200 = 99

Length of rectangle: Length of the rectangle is represent different values of the variables.
Example :                 here length of the rectangle for ( 200 -299 ) = 12 

Range of Rectangle: As per our understanding there is no particular definition for range of rectangle, But we have range of data as:
Range of data:         range of data is the lowest value and the highest value of data given as here.
Example:                 Range of data = 200 - 899