The symbol (element of) describes membership to a set. When reading an equation the symbol can be read as “in” or “belongs to”.
For example the above expression, , can be read as is an element of the set of real numbers, represented by the symbol .
The colon symbol is used in math to denote a condition for a statement. The symbol can be read as "such that" in a math expression.
A set is written with curly braces containing the elements of the set separated by commas.