Question: I am newby in LateX, but I want to create an stand alone document to be used as a equation library where I can select my equations by calling them by name, and finally produce a list of equations used in the working document, or a glossary with the equation and description. Thank you in advance.

Answer: 
can be improved for your needs

```
\documentclass[12pt]{article}
\usepackage{float}
\newfloat{EQN}{H}{eqn}
\begin{document}

\begin{EQN}
\begin{equation}
 y=f(x)
\end{equation}
\caption{my first equation}
\end{EQN}

\begin{EQN}
\begin{equation}
 y=f(x)
\end{equation}
\caption{my second equation}
\end{EQN}

\listof{EQN}{my equations}

\end{document} 

```

![enter image description here](https://i.stack.imgur.com/JcZcQ.png)
Based on Herbert's answer, with glossaries package:

```
\documentclass[a4paper]{article}
\usepackage{glossaries}

\usepackage{float}
\newfloat{EQN}{H}{eqn}

\newcommand\eqcite[1]{%
\begin{EQN}%
\begin{equation}%
\glssymbol{#1}%
\end{equation}%
\caption{\glsentryname{#1}}
\end{EQN}
}

\loadglsentries{glossdata.tex}
\makeglossaries

\begin{document}
\eqcite{eq1}
\eqcite{eq2}

\listof{EQN}{My equations}
\printglossaries
\end{document}

```

Your database is in file *glossdata.tex*

```
\newglossaryentry{eq1}{
   name={First equation}
  ,symbol={y=f(x)}
  ,description={Some equation}
}
\newglossaryentry{eq2}{
   name={Second equation}
  ,symbol={y=a+f(x)}
  ,description={Another equation}
}

```

To get list of descriptions, you have to run some indexing program, makeglossaries, makeindex or xindy. 

```
makeglossaries nameofyourdocument

```

![Equations, list of equations and glossary](https://i.stack.imgur.com/e42cv.jpg)