What are basic authentication headers?


I am new to ZuluTrade and I am trying to connect ZuluTrade api in python. I read the document but still got some questions. There’s one sentence saying that 'Each request needs basic authentication headers. '. I am not sure about what ‘basic authentication headers’ means.

I tried the following code:

result = requests.get(url=‘http://tradingserver.zulutrade.com/getInstruments’, headers={“ZuluAccountUsername”: “MyUserName”, “ZuluAccountPassword”: “MyPassword”})

But got the reply: <Response 411>

Can anyone tell me what are ‘basic authentication headers’? Or what’s wrong with my code?