The taxi driver suddenly stopped the vehicle after seeing a blind pedestrian in front of it.

In the given sentence, the word suddenly describes how an action takes place.

Hence, the word Suddenly is an adverb.

We often visit our grandparents who are living in New York.

In the given sentence, the word often describes when an action takes place.

Hence, the word Often is an adverb

The kid plays indoor games when they reach home.

In the given sentence, the word indoor describes where the action takes place.

Hence, the word Indoor is an adverb.