A Sefer Torah is the Torah text written by someone properly trained on a certain type of parchment and a certain kind of black ink. The Sefer Torah is hand written and costs tens of thousands of dollars.

The Torah is the content that is written in the Sefer Torah. It is the original Hebrew version of the Bible.

Sefer is Hebrew for "book". It's generally used specifically to mean the books of the Torah and associated rabbinical commentary.

The Torah (תורה) or Sefer Torah (ספר תורה)

The scroll that contains the 5 'books' of Moses is called the Torah.

It is called a Sefer Torah pasul, meaning a Torah scroll which is unfit for use. If the mistake is corrected by a sofer (scribe), it can be rendered fit again.