Google has created a single page where you can find all of the Google Search content policies. This includes Google Search's overall content policies, search feature policies and feature specific policies. You can find them all in this one document here.
Here is an overview of these policies but if you want to read each one, go to the above document:
Overall content policies for Google Search:
- Child sexual abuse imagery or exploitation material
- Highly personal information
- Spam
- Webmaster & site owner requests
- Valid legal requests
Search features policies:
- Advertisements
- Dangerous content
- Deceptive practices
- Harassing content
- Hateful content
- Manipulated media
- Medical content
- Regulated goods
- Sexually explicit content
- Terrorist content
- Violence & gore
- Vulgar language & profanity
Feature-specific policies:
- Autocompletes
- Dictionary boxes
- Featured snippets
- Google Discovers
- Google News
- Google Podcasts
- Image & video boxes
- Knowledge Graph & Knowledge Panels
- Structured datas
- Structured data for job postings
- User content on Search
I learned this news from John Mueller's news update video at the 6:56 mark where he said "we recently launched a shared location for all content policies around search. This should make it easier for you to find any specific policy that you're looking for."
Forum discussion at Twitter.