multiple mysql linked grids with EditableGrid

I am working through the EditableGrid demos modifying the code to understand it and reach a working example of multiple grids with the write-to-db example. I am a non-programmer and vba-hack.

Creating multiple grids in non-db examples is simple enough. However trying to replicate the code/structure for multiple grids I think prototype and this objects are might be confusing me

multiple grids without the db-link/inline-edit:

        window.onload = function() {
            editableGrid = new EditableGrid("DemoGridMinimal"); 
            editableGrid.tableLoaded = function() { this.renderGrid("tablecontent", "testgrid"); };
            editableGrid.loadXML("grid.xml");
            editableGrid = new EditableGrid("DemoGridMinimal2"); 
            editableGrid.tableLoaded = function() { this.renderGrid("tablecontent2", "testgrid"); };
            editableGrid.loadXML("grid.xml");
        }

single grid with the db link and inline edit: (a little modified from the example)

function DatabaseGrid() { 
    this.editableGrid = new EditableGrid("demo", {
        enableSort: false,
        tableLoaded: function() { datagrid.initializeGrid(this); },
        modelChanged: function(rowIndex, columnIndex, oldValue, newValue, row) {
            updateCellValue(this, rowIndex, columnIndex, oldValue, newValue, row);
        }
    });
    this.fetchGrid();   
}

DatabaseGrid.prototype.initializeGrid = function(grid) { grid.renderGrid("tablecontent", "testgrid"); };  
DatabaseGrid.prototype.fetchGrid = function() { this.editableGrid.loadXML("loaddata.php"); }; 

window.onload = function() { 
    datagrid = new DatabaseGrid();
};

if it helps put overall context, the end result is to have several grids on a single page, populated with single sql query, defined by a html form input {accounting sql injection}, with each grid showing different fields from the db

could someone be kind enough to briefly explain the context of prototype and this in the example here

done courtesy of freelancer.com.

with a "function DatabaseGrid()" to create each grid, a PHP call for each grid to populate them and a "$(document).ready(function()" listing each successive grid so each one loads on the webpage