Open bracket:

                      Open bracket is denoted by ( ) symbol. It means that the value of a variable lies in it.

Example: (1, 10) 

We take the value which is between 1 and 10 excluding 1 and 10.

If x∈ (1, 10) => 1 < x < 10

Closed Bracket:

                         It is denoted by the symbol [ ]. It means that value of a variable lies in it.

Example:  [1, 10]

Here we take the value which is between 1 to 10 including 1 and 10 also. 

If x∈ [1, 10] => 1 <= x <= 10

Some times these two bracket also used togather.

Example: let  1 < x <=10

then x∈ (1, 10]