what is the different between those two header "MainBaseNoStress" ,"MainVariantNoStress"

[kerolos]

MainBaseNoStress has a phone-set : B, C, D, G, N, R, S, T, Y, a, b, d, e, f, g, i, j, k, l, m, n, o, p, r, s, t, u, w, x , Howver
MainVariantNoStress has a phone-set : B, C, D, G, L, N, R, S, a, b, d, e, f, g, h, i, j, k, l, m, n, o, p, r, s, t, u, w

• what are those headers means ? and
• why there are different phone-sets ?
  Which one "MainBaseNoStress , or MainVariantNoStresshas or both" can i use for training ASR model (only after filter the raws have Yes is es coloum) only for spainish from spain ?