For most use cases, you should use TextField rather than the lower-level components that it delegates to (such as Input).
The relevant part of the documentation is here.
Particularly this line:
TextField is composed of smaller components ( FormControl, Input, FilledInput, InputLabel, OutlinedInput, and FormHelperText ) that you can leverage directly to significantly customize your form inputs.
The main reason to use these lower-level components is if you need to customize your form input in some way that isn’t supported using TextField.