All Chilli artificial bids are absolutely forcing, as you would expect.
1NT is always to play: it may not always be shape suitable or even promise a guard in their suit, but the bidder will not be surprised or distressed if partner passes.
Other than side-suit asks or responses in fit auctions, game bids and slam bids are always to play.
If there is already an agreed trump suit, a slam bid below that suit is an alternative slam suggestion. Because of Chilli's suit rules, long suits – especially minors – can often remain suppressed, and this will be the most common reason for making such a suggestion. Another possibility is that, having agreed a major, you now want to suggest playing in a previously undisclosed minor suit fit that may yield an extra trick.
NEXT: neutral auctions