The _dot product_ is an operation that takes two vectors in and outputs a single number (a scalar).

Here is how it works:

\\[
\begin{bmatrix}
1 & 2
\end{bmatrix}
\cdot
\begin{bmatrix}
10 & 20
\end{bmatrix}
=
1 \cdot 10 + 2 \cdot 20 = 50
\\]