One common way to define spontaneous symmetry breaking involves necessarily explicit symmetry breaking. We add explicit symmetry breaking terms to the Higgs potential, so that the spontaneous breaking of a global symmetry in multi-Higgs-doublet models is a particular case of explicit symmetry breaking. Then we show that it is possible to study the Higgs potential without assuming that the local gauge $SU(2)_L$ symmetry is spontaneously broken or not (it is known that gauge symmetries may not be possible to break spontaneously). We also discuss the physical spectrum of multi-Higgs-doublet models and the related custodial symmetry. We review background symmetries: these are symmetries that despite already explicitly broken, can still be spontaneously broken. We show that the CP background symmetry is not spontaneously broken, based on this fact: we explain in part a recent conjecture relating spontaneous and explicit breaking of the charge-parity (CP) symmetry; we also relate explicit and spontaneous geometric CP-violation.