Getting Information about Wolfram Language Objects
You can ask for information about any object, whether it is built into the Wolfram Language, has been read in from a Wolfram Language package, or has been introduced by you.
show information on Name
show extra information on Name
show information on all objects whose names begin with Aaaa
When you are using the Wolfram Language through the notebook-based interface, ?name gives you usage information with a link to the documentation for the function.
This gives information on the built‐in function Log:
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 the Wolfram Language can tell when you are requesting information rather than giving ordinary input for evaluation.
This gives information on all Wolfram Language objects whose names begin with Log. When there is more than one object, the Wolfram Language just lists their names:
?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, ?Lo* gets information on all objects whose names consist of the letters Lo, followed by any sequence of characters.
You can put * anywhere in the string you ask ? about. For example, ?*Expand would give you all objects whose names end with Expand. Similarly, ?x*0 would give you objects whose names start with x, end with 0, and have any sequence of characters in between. (You may notice that the way you use * to specify names in the Wolfram Language is similar to the way you use * in Unix and other operating systems to specify file names.)
You can ask for information on most of the special input forms that the Wolfram Language uses. This asks for information about the := operator: