Places where this is used include the global variables % and I.
The use of lazy in the name stems from the concept of lazy evaluation. The object the global variable is bound to will only be evaluated when called. The LazyGlobal property only holds once: after that, the result of evaluation is stored in the global variable, and it won't be reevaluated again:
In> a:=Hold(Taylor(x,0,30)Sin(x)) Out> Taylor(x,0,30)Sin(x); In> LazyGlobal(a) |
In> a:=Hold(2+3) Out> 2+3; In> a Out> 2+3; In> LazyGlobal(a) Out> True; In> a Out> 5; |