A “pictogram” or “pictograph” is a symbol used to represent an object, a place, an event or a concept with an illustration. It’s basically a form of writing in which ideas are transmitted through drawing. It is the basis of cuneiform writing which uses drawings as phonetic letters. An ideogram is a symbol which represents an idea. Pictograms were used by the ancient Chinese as early as 5000 BC. They predated the famous Sumerian cuneiforms in Mesopotamia. They were used to label basic farm produce as early as 9000 BC and with the rise of cities and spread of basic craftmanship they were used to label manufactured goods around 6000 BC. Amazingly pictograms are still in use as the main medium of written communication in some non-literate cultures in Africa, The Americas and Oceania. Below is an excellent example of some ancient pictograms.
Most of the letters of the Roman alphabet have their origins in pictograms. For example, the letter A represented the head of an ox, and if you turn it upside down, a bovine head with horns can be seen. Although written Chinese is often thought to consist of pictograms, less than 4% of all the characters ever created have a direct origin in pictograms.
Pictograms can often transcend cultures and countries because they can communicate to speakers of a many different languages. Road signs and other pictographic material (toilet, airport, train signs) are often adapted as global standards because they can be easily understood by all. There is also a standard set of pictograms used for laundry symbols and chemical hazard labels. Above you will see a great pictogram from an Australia zoo warning against swimming because of the threat of crocodiles.
Sources: answers.com, wikipedia
Cuneiform script is one of the earliest known forms of written expression. It was created by the Sumerians in about 3000 BC (over five thousand years ago!). It originally began as a system of pictographs, similar to, but more abstract than the Egyptian hieroglyphics. It was in use for almost 3,000 years. The last known cuneiform inscription was written in 75 AD.
Cuneiforms were usually written on clay tablets using a blunt reed for a stylus. The impressions left by the stylus had a “wedge” shape, which is where the name cuneiform comes from (the Latin word cuneus means wedge and the latin word forma means shape). The first images were drawn in vertical columns. Later people began to write in horizontal rows
Certain symbols were used to indicate the names of gods, countries, cities, vessels, birds, trees, etc. Individual words were represented by crude pictorial symbols that resembled in the some way the object being represented. However, as time passed and the script developed, many of the original pictographs began to lose their original function and a given sign could have various meanings depending upon the context. The number of symbols also began to be reduced as the writing became more phonological. Over time the pictorial representations became simplified and more abstract. The writing system underwent many changes. Images were often rotated and simplified many times. Eventually the system developed into a syllabic alphabet.

There is a great website called Write Like A Babylonian where you can type in your name and initials and a monogram will be created in cuneiform. You can see the results for my name and initials on the left.
The Sumerians lived along the lower Tigris And Euphrates valley in what is now Iraq. The were the fist people to build cities and achieve what we refer to as “civilization.” They domesticated goats and cattle, they grew wheat and barley, they baked bread and brewed beer. They also built large temples and had kings. But their biggest contribute to the world was the development of written language via cuneiform script. Cuneiform was also adapted by the Akkadins, Babylonians and Assyrians to write their own languages.
Sources: wikipedia, Washington State University, Penn Museum