How are acids and bases different?

Because an acid produces a hydrogen ion (H+) as it disassociates in water, while a base produces a hydroxide ion, (OH-) as it disassociates in water
Depends on the definition of acid and base.

Bronsted acid is a proton donor (HCl)

Lewis acid is a lone pair receptor (anything with an open orbital)

Bronsted base is a hydroxide donor or proton receptor (KOH)

Lewis base is a lone pair donor. (R-CN)