It means 'We are'
"sommes-nous ..." means 'are we ..' in French.
Sommes-nous .... means 'are we ...' in French.
"Nous sommes" means "we are" in English.
"sommes" is a form of the verb "être", to be."nous sommes" = we are.
Literally "Pourquoi sommes-nous parler français" reads as "why are we to speak French". If you mean "why should we / why do we have do speak French", this is: "pourquoi devons-nous parler français".
"nous sommes"
Nous sommes.
nous sommes voisins / nous sommes voisines (only if both neighbors are female)
'are we'
où sommes-nous ?
You can say "Où sommes-nous?" in French to ask 'where are we?'.
Nous sommes .... depuis .... means "we are ... since ..." Ex: nous sommes boulangers depuis 1980 (we are bakers since 1980)