Technology is not just about machinery, complex robotics, or software, as we know it today. In the Victorian era, even a societal change was classified as technological.
Production technologies are all about increasing your economic capacity in various ways. These tend to be very concrete inventions, such as Cotton Gin which increases the output of Cotton Plantations, and Dynamite which can be employed for increased yields in all kinds of Mines.
On some occasions, they are more abstract, such as Enclosure which is a prerequisite for the construction of modern, privately owned farms and ranches, or Shift Work which more effectively utilizes labor in your manufacturing industries. Production technologies also include advances to Railways, and some even unlock Goods unknown at the start of the game such as Rubber, Electricity, and Automobiles.
Military technologies improve your army and navy. These consist of a mix of new weapon technologies, doctrines, and ways of organizing your Servicemen and Officers. Rifling lets you switch Production Methods from Muskets to Rifles in your Arms Industries, increasing their Small Arms production.
Society technologies are all about new ideas for organizing society. These include ideas pertaining to politics, finance, and diplomacy to name a few. Democracy permits the enactment of various voting franchise Laws as well as Republican principles of governing. Pan-Nationalism is a requirement for forming certain larger countries and leads to Political Agitation which both makes your population more politically active and also gives you more Authority to deal with them, for example.