What does != "" mean in programming

I am just getting into a little php and programming and I would like to know what something like
If ($sMap != "") what does !="" mean and what does "" and " " on its own generally mean?

Thank you.
regsampAsked:
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dovidfCEOCommented:
Returns true if $x is not equal to $y, or they are not of the same type
regsampAuthor Commented:
And the "" is the $y?
Peos JohnPHPCommented:
1. != means "not equal to", (a!=b value of a is not equal to b),
2.  == means both are equal(a==b value of a and b are equal),
3. && means AND (condition 1 "and" condition 2 both are true)
4.|| means OR (condition 1 "or" condition 2 either on is true )
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regsampAuthor Commented:
I understand that but what does !="" mean? It is "not equal to" double quotes, space, nothing?
Peos JohnPHPCommented:
In your condition If ($sMap != "")

"" means empty, so this condition checks if $sMap value is NOT empty.

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regsampAuthor Commented:
That is what I thought. Thank you everyone. I am a newbie so I appreciate it.
Ray PaseurCommented:
If you're new to PHP and want to learn the language, this article can help.  Just skip over the parts you already know from other programming languages, work experience, or academic learning.
https://www.experts-exchange.com/articles/11769/And-by-the-way-I-am-New-to-PHP.html
regsampAuthor Commented:
Thank you very much for that link and the resources.
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