To govern something or somewhere means to have control over it and make decisions that affect how it runs.
When people talk about governing, they usually mean the actions of leaders in a country, city, or organization. For example, if you hear someone say "The government is trying to fix the economy," they're talking about the group of people who are responsible for making big decisions about how their country works. These decisions can be about things like laws, taxes, education, and even what services are available to citizens. Sometimes you might also hear about governing a company or an institution, where leaders try to make sure everything runs smoothly and according to plan.
How common is "govern"?
Word govern is considered uncommon in modern English. It has a balanced usage among all categories: speech, fiction, newspapers and academic texts.
Definitions
verb
(transitive) To make and administer the public policy and affairs of; to exercise sovereign authority in.
Example: The old king governed the land wisely.
(intransitive) To exercise political authority; to run a government.
(transitive) To control the actions or behavior of; to keep under control; to restrain.
Example: Govern yourselves like civilized people.
(transitive) To exercise a deciding or determining influence on.
Example: Chance governs the outcome of many card games.
(intransitive) To have or exercise a determining influence.
(transitive, obsolete) To handle, to manage, to oversee (a matter, an affair, a household, etc.).
(transitive) To control the speed, flow etc. of; to regulate.
Example: a valve that governs fuel intake
(transitive, obsolete) To direct the course of, to guide in some direction, to steer.
(transitive, obsolete) To look after, to take care of, to tend to (someone or some plant).
(transitive, obsolete) To manage, to control, to work (a tool or mechanical device).
(transitive, grammar) To require that a certain preposition, grammatical case, etc. be used with a word.