The word "lexicography" comes from Greek roots meaning "the study of vocabularies." According to the Merriam-Webster Dictionary. it has been in use at least since 1680, but arguably lexicography has been practiced since the first Indian, Arabic and Chinese dictionaries were being written 4,000 years ago. Back then, lexicography was not practiced by linguists, but by priests who had to understand and interpret ancient and difficult texts.
Theoretical lexicography, sometimes called lexicology, is the branch of linguistics that discusses the solutions of the problems inherent to the creation of dictionaries.
You could think that there is not much to making a dictionary, or that all the problems would have been solved in the centuries since the publication of Robert Cawdrey's "A Table Alphabeticall," the first English dictionary, in 1604. However, the constant evolution of languages and technologies together with the demands of globalization keep posing new challenges to dictionary editors everywhere.
Practical lexicography is the actual art and craft of writing an actual dictionary. Lexicographers cannot just think of a really big list of words and make up their definitions.
Among many other activities, a practical lexicographer must identify and profile the target audience, define the specific functions of the dictionary, choose the appropriate structures for presenting the data, design the most efficient means for the location and access of specific terms in printed and electronic formats and, yes, define the words.
There are several associations and journals specializing in lexicology, including: the Dictionary Society of North America, the European Association for Lexicography with its counterparts the Afrilex and the Australex, and the International Journal of Lexicography.
Taking a look at their current concerns, one can find discussions about the creation of legal dictionaries when both the terminology and the actual legal process differs between countries, the use of software for the automatization and standardization of dictionary-making, the use of multimedia and animations in dictionaries, and several similar emerging problems brought forth by technology and globalization.
Some lexicographers have become household names in the countries where their dictionaries are sold.
Paul Robert's dictionary is often called "Le Robert" in France. Similarly, Pierre Larousse is well known in France and Latin America, while in the United States the name of Noah Webster is well-known because of his work on the Merriam-Webster dictionary.
Not every dictionary, however, is named after the lead lexicographer. George Merriam, for example, was not a lexicographer, but a publisher.