These are the individual projects that make up the Yocto Project. Each of these holds a key role in developing embedded Linux, and the Yocto Project works to make all of them interoperable and useful.
When building software it can be necessary to perform operations as if you were the system administrator. For example, you might need to define a file's ownership or permission information.
Pseudo is a program that can either be used directly or as an LD_PRELOAD, which allows these operations to succeed as if the user did have system administrator privileges even though they are an ordinary user.
Pseudo has a lot of similarities to fakeroot but is a new implementation that improves on the problems seen using fakeroot. Pseudo is now extensively used by Poky as a replacement to fakeroot but can also be used standalone in many other use cases.