Question about simple SRAS and AD curve Does the general price level show the aggregate of all goods &amp; services demanded or supplied at a certain price or does it show something else entirely?

My knowledge of economics is still very much in its infancy, so only plain language in answers please!
General price level is defined by the price that you pay for a basket of goods. This basket of goods is decided on the basis of general consumption patterns in the economy and includes a number of sectors (with a number of items) like food, transport, medical care, etc. Such baskets can be defined differently to arrive at different measures of general price levels such as the one faced by end consumers or wholesale buyers. 

In a nutshell, it gives an idea of how the prices in the economy are moving. So, price of a good A might increase while price of good B might decrease but it may so happen that the general price level may increase or decrease depending upon the defined basket and the weights assigned to the items in basket.