Questions & Answers about זה מושג חשוב.
Because in Hebrew, the verb to be is usually omitted in the present tense in sentences like this.
So:
זה מושג חשוב
literally looks like this / concept / important
but it naturally means:
This is an important concept.
If you change to past or future, Hebrew does use a form of to be, for example:
זה היה מושג חשוב = This was an important concept
זה יהיה מושג חשוב = This will be an important concept
Here, זה means something like this or this is at the start of the sentence.
In sentences of this type, זה often introduces or identifies something:
זה ספר = This is a book
זה רעיון טוב = This is a good idea
Depending on context, English might translate it as this or sometimes it, but the basic Hebrew word is still זה.