When partner opens one of a suit, the Baron 2NT response shows a strong balanced hand. It denies a 5-card suit or 4-card support for partner.
Some players use Baron as 16-18 HCP. Others prefer it to be 16+.
Either way, it encourages the partnership to locate a 4-4 fit without bypassing 3NT.
As a corollary, a 3NT response shows 13-15 HCP. Thus the natural meanings of 2NT and 3NT are inverted to facilitate slam exploration at the 3-level.
Opener rebids 3NT with a balanced minimum. She may have a 4-card major.
Opener rebids a new 4-card suit (up the line) with slam interest.
Opener rebids her 6+ card suit.
Showing a minimum
Bidding 4-card suits up the line with slam interest