In Cells
" is simply a double quote mark and has no relevance
eg: abc"abc is the text string abc"abc
' is used in a cell to force the contents to be treated as text not numbers
eg: '0123 displays as 0123 not as 123
in Formula
" is used to mark the start and end of text
eg: =concatenate("Hello", " ", "AmplifyHope")
will display Hello AmplifyHope
' is just a text character