Wordlist type and difference

What is the difference between <input.USER><input.PASS> and <input.USERNAME><input.PASSWORD>?

And why doesn’t the default word list type work?

when you going to use default wordlist you need to add <input.DATA> in your config , other then <input.USER> and <input.USERNAME>
<input.PASS> and <input.PASSWORD> this both just shorter form nothing special for wordlist credentials