FROST's distributed key generation involves N parties each creating a secret polynomial, and sharing evaluations of this polynomial with other parties to create a distributed FROST key.
The final FROST key is described by a joint polynomial, where the x=0 intercept is the jointly shared secret s=f(0). Each participant controls a single point on this polynomial at their participant index.
The degree T-1 of the polynomials determines the threshold T of the multisignature - as this sets the number of points required to interpolate the joint polynomial and compute evaluations under the joint secret.
T parties can interact in order to interpolate evaluations using the secret f[0] without ever actually reconstructing this secret in isolation (unlike Shamir Secret Sharing where you have to reconstruct the secret).