It is conveying your state of mind in an effort to demonstrate politeness or tact.
"I wonder if you could help me find my size" is the same thing as "would you please help me" but slightly less assertive and demanding.
In some cases you are simply conveying your state of mind with no specific intent.
"I wonder if it is going to rain" In this case you are stating what you are thinking but want nothing. You may not even really expect an answer so it would be a rhetorical question in that instance.
Wondering is the key word,
1-Desire or be curious to know something.
2-Used to express a polite question or request: "I wonder whether you have thought more about it?
Source(s):
Dictionary.com - Answers.com - Merriam-Webster - The Free Dictionary