I understand the 2 words are very simple words in English until I came across this sentence below:

"Please drive slow".

I know it should be an adverb here, and I checked it up to find "slow" is not only an adjective, but also an adverb. So my wondering is how to differentiate "slow" from "slowly" both as adverbs? For the sentence above, which sounds a bit weird though, is it also ok to say "Please drive slowly"?