double negative

Negatives are words like not, never, nowhere, no-one, no more, nobody

he doesn't like anyone

you will never win

he's not going anywhere

Double (and sometimes even triple!) negatives are not necessary but are often heard, maybe for comic effect or for emphasis and are often heard in song lyrics eg

"you don’t want me no more" which should be "you don't want me any more"

it ain't gonna worry me no more

you won't win nothing

no-one never comes here no more

Test yourself

Put into correct written English:

1. You're not getting nothing.
2. No-one comes here no more.
3. Don't you tell nobody. (Rod Stewart song) 
4. Never buy nothing from him.

Answers

1. You're not getting anything. or You're getting nothing.
2. No-one comes here any more. or No more do people come here. (the latter is more a poetic style than every day speech)
3. Don't (you) tell anybody. or Tell nobody.
4. Never buy anything from him. or Buy nothing from him (ever).