What is Dirac Notation?

Introduction to Quantum Computing

"Dirac notation, also called bra–ket notation, is a way to write objects in linear algebra."

A qubit drawn as |𝜓⟩  is called a “ket”.  The vertical bar “|” and the right angle bracket “⟩” come together to form the ket which represents a vector in a particular complex linear space. These are used to help simplify the writing of long, complex vectors.  So this can be written as |φ>

When the rows are swapped for columns for the vector, while not vectors, they can be placed in a one-to-one correspondence with them. They are called “bras”, and are written as "⟨ |", with an appropriate label as needed. This can be written as <θ|