Alkyl halides (or tosylates) will react with hydroxides ions to give alcohols. This is an SN2 reaction.
Alcohol formation (HO‾) Explained:
In this reaction, as in any SN2 reaction, we have a substrate (butyl bromide), a leaving group (bromide), and a nucleophile (hydroxide ion). If you have NaOH, the reagent in that reaction is actually a hydroxide ion (HO‾). Na+ is the counter-ion and its role in the reaction does not concern us in most cases.