A corporation's annual report is usually a colored, professionally presented, and marketable document intended for an audience of shareholders.
10-K:
The 10-K report is submitted to the SEC in a generic format, with no pictures or charts. The SEC has very strict guidelines on what information must be included and how it must be organized.
Source: https://www.investopedia.com/ask/answers/102714/what-are-dif...
Edit: I'm glad to see this is the #1 post on HN (at the time of this writing) even though the author, like many individual and some institutional investors, innocently do not know the difference between a company's PR-like annual report and an SEC-audited 10-K form. Hopefully the upvotes will draw attention to this common misconception which is also discussed by the SEC:
https://www.investor.gov/introduction-investing/investing-ba...
Disclosure / Shameless Plug:
I run https://Last10K.com which is an SEC.gov alternative for investors to find and read 10Ks more efficiently.