GitLens is an open-source extension created by GitKraken that assists you in better understanding code. It offers insight at who, why, and when a line or code block was updated.
An interesting feature is, The Visual File History, which allows you to analyze the evolution of a file with all the relevant facts, such as changes, size, and authors, and so on. Worktrees is a feature that seeks to make developers' lives easier by allowing them to check out many branches at once, each in its own window or all together in the same workflow.
It also provide many other interesting features that would simplify developemnt process like authorship code lens, On-Demand File Annotations, revision navigation, current line blame, Git Command Palette, terminal links and others.
You can learn more from the official site: https://www.gitkraken.com/gitlens