What it means
ということだ is used after a plain clause to summarize, restate, or explain its meaning. It often corresponds to “that means...” or “in other words, ...” and presents the preceding information as a conclusion or interpretation. The polite counterpart is ということです.
Usage note
Depending on the context, ということだ can also report information heard from someone else, similar to “I hear that...” or “it is said that...”. When the preceding predicate is a noun or a な-adjective, retain だ before ということだ, as in 静かだということだ.
How to use it
Clause (plain form)ということです
会社は来月から在宅勤務を始めるということです。
That means the company will start working from home next month.
Clause (plain form)ということだ
会社は来月から在宅勤務を始めるということだ。
That means the company will start working from home next month.