Two weeks (a period of 14 days). A common time expression used in everyday speech and writing.
来週から二週間、海外へ出張に行きます。
I'll be on a business trip abroad for two weeks starting next week.
その薬は二週間服用すると効果が出ることが多い。
That medicine often shows effects after two weeks of taking it.
二週間後に試験があるから、計画的に勉強しよう。
There is an exam in two weeks, so let's study in a planned way.