Protected is an attribute which prevents any values associated with a symbol from being modified.
ReadProtected is an attribute that prevents values associated with a symbol from being seen.
Protect
(Built-in Mathematica Symbol) Protect[s_1, s_2, ...] sets the attribute Protected for the symbols s_i. Protect["form_1", "form_2", ...] protects all symbols whose names match any of the string patterns ...
Locked
(Built-in Mathematica Symbol) Locked is an attribute that, once assigned, prevents modification of any attributes of a symbol.
Unprotect[s_1, s_2, ...] removes the attribute Protected for the symbols s_i. Unprotect["form_1", "form_2", ...] unprotects all symbols whose names textually match any of the ...
Copyable is an option for Cell that specifies whether a cell can be copied interactively using the front end.
AbortProtect[expr] evaluates expr, saving any aborts until the evaluation is complete.
Definitions such as f[x_]=x^2 specify values for functions. Sometimes, however, you need to specify general properties of functions, without necessarily giving explicit ...
Any Mathematica symbol can have both a variety of types of values, and a variety of independently settable attributes that define overall aspects of its behavior.
Mathematica makes it easy to "bulletproof" packages, and prevent features of their environment from affecting their internal operation.