Baron is reached only by the sequence:

1X - 2NT
With NO opponent intervention

It shows 16+HCP and a balanced hand - NO 5 card suits

It invites the partnership, starting with the opener to bid 4 card suits 'up the line'

Taking the suits from Clubs upwards a four card suit is bid and in the case of Opener he may rebid his opening suit if it is 5 cards. Responder may show a four card suit or 3 card support for opener's suit.
1 - 2NT - 3NT - PASS : shows opener's distribution to be 3433 precisely
1 - 2NT - 3 - 3 - 3NT... Shows opener's distribution as 5-4  Hearts and Diamonds & responder has shown 4 card Heart support.
If responder continues with 4NT: this is Quantitative.