Difference between subset and belong What is the difference between subset and belong to ??
And why : A subset A is always true and : A belong to A is not true ??

$A$ is a subset of $B$ means that every element of $A$ is also an element in $B$.
$x$ belongs to $A$ if $x$ is an element of $A$ itself.
Example:
$A = \{1, 2, 3\}$ is a subset of $B = \{1, 2, 3, 4\}$, because $1,2$ and $3$ are all elements of $B$.
However, $2$ belongs to $B$, and $4$ does not belong to $A$.
