1.We use you to talk about people in general including the speaker and the hearer
我们通常用you来谈论人们,包括说话者和听者:

You can buy this book anywhere > This book is on sale everywhere.

You can’t park here > Parking is not allowed here.

They don’t let you smoke in here > No smoking here.

2.We use they or them to talk about people in general: 
我们通常也用they或者them来谈论人们:

They serve good food here.

Ask them for a cheaper ticket.

3.… especially about the government and the authorities:
特别是关于政府或者权威

They don’t let you smoke in here.

They are going to increase taxes.

They are building a new motorway.

They say it’s going to rain tomorrow.