What does it mean?
Taken over
You have taken over at piece of land
Dominating
You can be dominating (You like to choose everything)
Established themselves
They have build up something or settle down at a place
Colonial power
You have power over your colonials
Trading route
Its a route where you sail or drive to trade stuff.
The slave trade
Its a trade where you trade slaves
Colonised
Another country has taken over your country
Initial plan
Your first plan or the main plan
Ruled
You are the power aka the ruler
Regain their independence
A country have gained their independence back after losing it.
Convenient
Its practical