help with regular expression

Can anyone tel me what this regular expression allows?  I know it allows a-z, both lower and uppercase, a length of 1 to 50, and spaces.  What does the ''-' part mean?  

"^[a-zA-Z''-'\s]{1,50}$"
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HLRosenbergerAsked:
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Éric MoreauSenior .Net ConsultantCommented:
isn't it the - characters:
any letters
-
any with space (\s)
allow repeat pattern 1 to 50 ({1,50})
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HLRosenbergerAuthor Commented:
Also, if I do this :   "^[a-zA-Z\s\-\']{1,50}$"

This mean in addition to a-z (upper or lower),  spaces, hyphens and single quotes are allowed, correct?
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HLRosenbergerAuthor Commented:
how does this:

''-'  

mean the same as this:

/'
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it_saigeDeveloperCommented:
Your original regular expression literally means this:

From the start of the string (^),
match a single character from the following list (a through z, A through Z, ', ' through ' and any whitespace character),
as many times as possible; giving back as needed; 1 to 50 times ({1, 50}).

As such your original regular expression can also be rewritten as:

"^[a-zA-Z'\s]{1,50}$"
"^[a-zA-Z\'\s]{1,50}$"
"^(?i)[a-z''-'\s]{1,50}$"
"^(?i)[a-z'\s]{1,50}$"
"^(?i)[a-z\'\s]{1,50}$"

Which all mean the same thing as above.

-saige-
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HLRosenbergerAuthor Commented:
Saige thanks!

So the escape char is backslash correct?     How is this ''-' the same as \'  ??

And what does (?i) mean?
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it_saigeDeveloperCommented:
''-' is two single quotes, hyphen and one singe quote.

When an un-escaped character is used, the regular expression means literally the un-escaped character (unless that character must be escaped in order to match on it; e.g. the \ must be escaped to match on it, \\ means match a single \, literally).

That being said:
' means match the character ', literally.
['-'] means match a single character in the group ' through '.
\' means match the character ', literally.  The \ is the escape character and not needed since ' does not need to be escaped.

So the three examples above will match a single '; one time.

As for (?i); this means that whatever follows is matched without case sensitivity.

You can test this at https://regex101.com/.

-saige-
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HLRosenbergerAuthor Commented:
Thanks so much!
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