Not sure what you mean by plot.
In the case of a CHART, you can click on any point in your graph, it will show you the data series associated to your graph.
In the case of a CELL, select Formulas>Trace Precedents (or Dependents) to find related cells.
In the same section of your tab, you can also select "Show Formulas". This will change the view of all your cells containing formulas to the actual formula itself. One function I like to use with my students is the =FORMULATEXT() function. It allows you to create a function right next to the calculated cell explaining how the formula is built without having to edit it.
Hope that helps!
