The VBA Help blog

Sometimes you don't know until run time which method to call ... the name's sitting in a cell, a file, a registry key or a button's Tag. VBA's CallByName turns that String into a call: getting or setting a property, or calling a method, by name.

Expanding and unexpanding environment strings using the Windows API.

Often, especially when creating text to show to a user in a dialog, I have a Collection or Array of Strings that I want to use to inform the user of some information. Code to compile those Strings into "clean" user-friendly text can be a pain to write ... for example, making sure the penultimate and last items are delimited by "and" instead of a comma especially when you don't know how many Strings will be included from the off.

Interpolation means 'inserting one thing into another'. In this case, inserting one (or more) 'sub' Strings into another 'main' String.