example_overlay.tex

\begin{figure}[h]
    \vspace{\baselineskip}
\begin{minipage}{0.5\columnwidth}
\begin{equation*}
\label{eq:ab_flushing}
N_{i} = 
\color{purple}
\overbrace{ 
    \tikzmarknode{qp}{\highlight{purple}{ \color{black}  $Q_p$ }} \color{black}\big( \tikzmarknode{tj1}{\highlight{NavyBlue}{ \color{black}  $t_{j+1}$}} \color{black} - \tikzmarknode{tj}{\highlight{Bittersweet}{ \color{black} $t_{j}$}}  
    \color{black}\big) |   
    \tikzmarknode{aj}{\highlight{purple}{ \color{black}   $\forall j$ }}
    \color{black}\big)
}^{\substack{\text{\sf \footnotesize \textcolor{purple!85}{Some annotation about the 
	}} \\ \text{\sf \footnotesize \textcolor{purple!85}{entire equation here.
}} } }
\end{equation*}
\vspace*{0.5\baselineskip}
\begin{tikzpicture}[overlay,remember picture,>=stealth,nodes={align=left,inner ysep=1pt},<-]
% For "t_{j+1}"
\path (tj1.north) ++ (-3.85,-1.8em) node[anchor=north west,color=NavyBlue!85] (tj1text){\textsf{\footnotesize property of (j+1)\textsuperscript{th} item}};
\draw [color=NavyBlue](tj1.south) |- ([xshift=-0.3ex,color=NavyBlue]tj1text.south west);
% For "t_{j}"
\path (tj.north) ++ (0.3,-1.8em) node[anchor=north west,color=Bittersweet!85] (tjtext){\textsf{\footnotesize j\textsuperscript{th} item}};
\draw [color=Bittersweet](tj.south) |- ([xshift=-0.3ex,color=Bittersweet]tjtext.south east);
\end{tikzpicture}
\end{minipage}
\hfil
\begin{minipage}{0.5\columnwidth}
\begin{equation*}
    \label{eq:ab_crypto}
    \hspace*{-6em}
    X_{i} = \frac{1}{\sum_{i=1}^{\tikzmarknode{n}{\highlight{purple}{N}}} 
    \sum_{j=1}^{\tikzmarknode{mi}{\highlight{NavyBlue}{$M_i$}}} 
    \tfrac{\tikzmarknode{lij}{\highlight{Bittersweet}{$l_i^j$}}}{\tikzmarknode{lmax}{\highlight{OliveGreen}{$l^{max}$}}}
    }
\end{equation*}
\vspace*{0.8\baselineskip}
\begin{tikzpicture}[overlay,remember picture,>=stealth,nodes={align=left,inner ysep=1pt},<-]
    % For "N"
    \path (n.north) ++ (0,1.8em) node[anchor=south east,color=Plum!85] (ntext){\textsf{\footnotesize number of objects}};
    \draw [color=Plum](n.north) |- ([xshift=-0.3ex,color=Plum]ntext.south west);
    % For "M_i"
    \path (mi.north) ++ (0,3.5em) node[anchor=north west,color=NavyBlue!85] (mitext){\textsf{\footnotesize number of other objects}};
    \draw [color=NavyBlue](mi.north) |- ([xshift=-0.3ex,color=NavyBlue]mitext.south east);
    % For "l_i^j"
    \path (lij.north) ++ (0,1.9em) node[anchor=north west,color=Bittersweet!85] (lijtext){\textsf{\footnotesize size of j\textsuperscript{th} service}};
    \draw [color=Bittersweet](lij.north) |- ([xshift=-0.3ex,color=Bittersweet]lijtext.south east);
    % For "l_i^max"
    \path (lmax.north) ++ (-2.7,-1.5em) node[anchor=north west,color=xkcdHunterGreen!85] (lmaxtext){\textsf{\footnotesize maximum obj size}};
    \draw [color=xkcdHunterGreen](lmax.south) |- ([xshift=-0.3ex,color=xkcdHunterGreen]lmaxtext.south west);
\end{tikzpicture}
\end{minipage}
\caption{Two Equations side-by-side using minipage and figure constructs.}
\end{figure}