good / well
The adjective versus the adverb.
Good is the adjective: a good lock. Well is the adverb: the lock works well. After a linking verb—such as be, feel, look, taste, smell, sound—use the adjective: I feel good. As an adjective, well means healthy: I feel well.
Examples
Use The new varnish looks good on the oak table.
Use The old pump still runs well.
Avoid The old pump still runs good. (Change good to well.)