, ... ] clears values and definitions for the .
", ... ] clears values and definitions for all symbols whose names match any of the string patterns .
Clear does not clear attributes, messages, or defaults associated with symbols.
"] allows metacharacters such as *, as specified in Section A.3.13.
`*"] clears all symbols in a particular context.
Clear is HoldAll.
Clear does not affect symbols with the attribute Protected.
See the Mathematica book: Section 1.2.2, Section 1.7.1, Section 2.4.3, Section 2.6.12, Section A.5.4.
See also: Remove.
Various rules and values are associated with h1.
Here are the rules in action.
Clear gets rid of values and definitions from h1.
The Listable attribute is left alone by Clear.
To get rid of values alone use Unset; to get rid of everything use ClearAll; to get rid of everything including the symbol h1 itself use Remove.