|?Name||show information on Name|
|??Name||show extra information on Name|
|?Aaaa*||show information on all objects whose names begin with Aaaa|
When you use to get information, you must make sure that the question mark appears as the first character in your input line. You need to do this so that Mathematica can tell when you are requesting information rather than giving ordinary input for evaluation.
?Aaaa will give you information on the particular object whose name you specify. Using the "metacharacter" , however, you can get information on collections of objects with similar names. The rule is that is a "wild card" that can stand for any sequence of ordinary characters. So, for example, gets information on all objects whose names consist of the letters , followed by any sequence of characters.
You can put anywhere in the string you ask about. For example, would give you all objects whose names end with Expand. Similarly, would give you objects whose names start with , end with , and have any sequence of characters in between. (You may notice that the way you use to specify names in Mathematica is similar to the way you use in Unix and other operating systems to specify file names.)