Trailing space is all whitespace located at the end of a line, without any other characters following it. This includes spaces (what you called a blank) as well as tabs \t , carriage returns \r , etc. There are 25 unicode characters that are considered whitespace, which are listed on Wikipedia.

What is a trailing whitespace?

Trailing whitespace is any spaces or tabs after the last non-whitespace character on the line until the newline.

Is trailing whitespace bad?

Additionally, trailing whitespace serves no purpose and adds unnecessary diffs in commits.