In essence, Delphi knows two ways of passing parameters to a method (or procedure, or function, or anonymous method, it's all the same). Parameters can be passed by value or by reference.
The former makes a copy of the original value and passes that copy to a method. The code inside the method can then modify its copy however it wants and this won't change the original value.
The latter approach doesn't pass the value to the method but just an address of that value (a pointer to it). This can be faster than passing by value as a pointer will generally be smaller than an array or a record. In this case, the method can then use this address to access (and modify) the original value; something that is not possible if we pass ...
