What is the purpose of "!" and "?" at the end of method names?

It's "just sugarcoating" for readability, but they do have common meanings:

• Methods ending in ! perform some permanent or potentially dangerous change; for example:
  • Enumerable#sort returns a sorted version of the object while Enumerable#sort! sorts it in place.
  • In Rails, ActiveRecord::Base#save returns false if saving failed, while ActiveRecord::Base#save! raises an exception.
  • Kernel::exit causes a script to exit, while Kernel::exit! does so immediately, bypassing any exit handlers.
• Methods ending in ? return a boolean, which makes the code flow even more intuitively like a sentence — if number.zero? reads like "if the number is zero", but if number.zero just looks weird.

In your example, name.reverse evaluates to a reversed string, but only after the name.reverse! line does the name variable actually contain the reversed name. name.is_binary_data? looks like "is name binary data?".

Question mark indicates that the method returns boolean. Already answered here:

What does the question mark operator mean in Ruby?

The bang indicates that the method acts on the object itself. Already answered here:

Why are exclamation marks used in Ruby methods?

In Ruby the ? means that the method is going to return a boolean and the ! modifies the object it was called on. They are there to improve readability when looking at the code.