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Getting Information about Mathematica Objects
You can ask for information about any object, whether it is built into Mathematica, has been read in from a Mathematica package, or has been introduced by you.
| ?Name | show information on Name |
| ??Name | show extra information on Name |
| ?Aaaa* | show information on all objects whose names begin with Aaaa |
Ways to get information directly from the Mathematica kernel.
When you are using Mathematica through the notebook-based interface, ?name gives you usage information with a link to the documentation for the function.
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.)
