Who is the president of a university? Sorry if the question is weird but I have not seen this terminology before. Who is the president of a university?

In my country, a rector is the leader of a university. A dean might run a faculty, possibly containing several departments. A department head is in charge of a single department.
This is just a different word for the most senior executive of a university. There are many names for this position. In the UK alone they may be called (most commonly) the vice-chancellor, the principal or the president. Broadly speaking, countries where universities are operated by the state have more consistent names for positions in the hierarchy, whereas countries where they are independent organisations have more of a diversity of names.