Curious marker

[PT]

I noticed on a document I was composing that occasionally some curious
"objects" appear in blue beneath certain text. For example, under the word
"I'll", a thin rectangle blue rectangle appears under the I and apostrophe.
What could be doing this. Is it friend or foe?

 

[Suzanne S. Barnhill]

See the Help topic "I see something unusual in my document."

 

[Deborah Jean]

Blue or other color underline
When you automatically check the consistency of your formatting, Word uses
wavy blue underlines to indicate possible instances of inconsistent
formatting.