The vertical bar symbol is used in math to represent the absolute value operator. Typically the symbol is used in an expression like this:
In plain language, this means take the absolute value of the value which is equal to .
To vertical bars on either side of a vector represent taking the magnitude or length of that vector
The notation for taking the absolute value is two vertical lines on either side of the expression being evaluated.
The syntax for a determinant is to vertical bars on either side of the matrix.
The conditional probility formula shows how to calculate the probability of a event B, given that another event A has already occured.