These are the (so-called "general purpose") registers in the x64 architecture:
(Image taken from this video.)
In x64 (or x86_64) archtecture, the registers have a size of 64 bits or 8 bytes each. As we can see, each register is also divided into smaller parts. Take for example the RAX register, which is a whole 64-bit register. The lower half of RAX is called EAX and it can be treated more or less like a register itself. EAX has 32 bits or 4 bytes. Similarly, the lower half of EAX is AX, a 16-bit register (or 2 bytes). AX is divided into 2 registers: AL (the lower 8-bit register) and AH (the higher 8-bit register).
The lower halfs of the registers on the left side of the picture already existed in the previous 32-bit x86 archtecture. They have been expanded to 64 bits, and moreover, all the other registers on the right side of the picture have been added.
All these registers can be used by us in our assembly code, but we will see later that some of those (like RIP and RFlags) are not really general purpose.