pojedynczy znak cudzysłowu

The single quotes seem to indicate thoughts formulated in words.

Literal syntax is a single quote followed by the symbol name.

If I left out the single quotes, the glob could potentially be expanded by the shell.

It is written as a symbol similar to the apostrophe or opening single quote.

However, atoms containing spaces or certain other special characters must be surrounded by single quotes.

For single quotes or apostrophes leave out the Shift key.

Note that single quotes were used above to quote the string.

For example by setting it in single or double quotes:

Character literals ('M - leading single quote) are also allowed.

Either single or double quotes can be used to quote strings.