Having difficulty to understand the implication of the big parentheses in an equation

Question

What do the big parentheses imply in the following equation?

\begin{equation} \nabla f(\upsilon^{k},\gamma^{k})^T \left( \begin{array}{ll} \upsilon - \upsilon^{k} \\ \gamma - \gamma^{k} \end{array}\right) + f(\upsilon^{k},\gamma^{k}) \leq \alpha, \forall (\upsilon^{k},\gamma^{k}) \in U \end{equation}

I want to know how I should interpret the following part in the formula: \begin{equation} \left( \begin{array}{ll} \upsilon - \upsilon^{k} \\ \gamma - \gamma^{k} \end{array}\right) \end{equation}

Answer 1

The parenthesis around

\begin{equation} \left( \begin{array}{ll} \upsilon - \upsilon^{k} \\ \gamma - \gamma^{k} \end{array}\right) \end{equation}

represent a column vector of coordinates

$$v-v^k$$

and

$$\gamma-\gamma^k.$$