In Spanish, the letters B (be, be larga o be grande, depending on the country) and V (uve, ve corta o ve chica, depending on the country) don’t have any phonetic difference, like the ones they have in other languages (English for example).

In a simple way, they’re pronounced the same way. Their sound is very similar to that of the English B. When either letter is between to vowels, their sound can somewhat resemble the one of the English V, but Spanish speakers will not make the sound by touching the lower lip with the upper teeth. Instead they will make it by always touching the upper and lower lip.

One consequence of this is that it is not rare for Spanish speakers to have spelling difficulties with words that have B or V, because there is no way for them to differentiate them from their sound.

Vaca, bote, jabón, envidia (there are no words in Spanish that have a B right after an N), balde, cambio, (M and V can never be togheter) are some examples.