This naturally confuses beginners because the concept of registers is completely foreign to other editors. Emacs can provide similar functionality, but by that point Vim is no longer in "weird" mode compared to what you know. We do a lot of simplification when talking about Vim, but small points like this can be immensely confusing for people who just want something to behave the way they're used to.
> The unnamed register is the default and holds the most recently deleted or yanked text; it’s what’s called upon when you just type p without specifying a register.
Source: https://pbrisbin.com/posts/vim_registers/
Besides + there is also * for accessing alternate clipboard: http://vim.wikia.com/wiki/Accessing_the_system_clipboard