Aloo is a common word for potato in many languages in India and South Asia, coming from the Sanskrit ālu. It originally meant 'root vegetable' or 'yam', but potatoes won the culture war, and you will now rarely find a yam dish referred to with the label aloo; if you do, it will probably actually use sweet potato, not a yam.
In the English speaking world 'aloo' is most often used to refer to Indian dishes containing potato as one of their primary ingredients, e.g., aloo gobi, meaning potatoes with cauliflower, or aloo paratha, meaning a flatbread made with potatoes.
However, there is one major exception to this: vindaloo is a coincidental convergence, derived from the Portuguese "vin d'alho" (literally, 'wine and garlic sauce', although today the wine is often replaced with vinegar). Traditionally vindaloo does not contain potatoes, although the coincidence of the name has caused some people to add them for semantic consistency.