I have some weird bootloader looking screen. says Downloading do not turn off target but I cant do anything on iy has the android with start over his head but pressing power doesnt do anything.
Odin mode is the download mode Samsung puts your phone in order to do the equivalent of an SBF for a Moto device. Its another way to return your device to stock. But since its a Nexus, you can just use fastboot to do that.
As for your issue, what did you do right before this happened? Did you flash a new kernel? Did you enable a fast charge toggle?