When you go into the Faction Creator (Main Menu/Workshop), there are some techs which you can customize your faction to begin the game with. These techs are Kingdom and Empire specific. Kingdom and Empires have their own tech trees. So if you customize your faction to have an Empire tech, but you choose to play as a Kingdom, you will not receive the Empire tech. To get the Empire techs you must play an Empire faction, and vic versa.
I've researched which techs belong to who, and what benefits they grant. Thought I'd share...
Kingdom
Civilized ~ Grants the Civics tech located within the Civilization branch
Allows the building of School, Market, Library
Weathered Warriors ~ Training tech / Warfare branch
Allows the training of Experienced units
Adepts ~ Arcane Research / Magic
Allows the building of Monastaries and Arcane Temples
Wanderlust ~ Exploration / Adventure
Reveals new resources
Entrepreneurs ~ Trading / Diplomacy
Allows Caravans and unlocks trading with other factions
Empire
Habitation ~ Proper Living tech located within the Emperium branch
Allows the building of Imperial Throne and Shanty
War Machine ~ Tools of War tech / Conquest branch
Unlocks Soldiers Cloak, Padded Grieves and Cuirass, Leather Helm, Light Wood Shield, Axe, Boar Spear, Fang Dagger
Allows the building of the War Council
Cartographers ~ Mapping / Domination
Reveals Notable Locations and "awakens more dangerous creatures"
Darkling Ambassader ~ Reunion / Cooperation
Allows the building of Darkling Camps
note: Normal building pre-reqs still apply (ie city size)