PlayerInputPacket and SetEntityLinkPacket

SetEntityLinkPacket is packet when player click on boat or minecart (I think)

but what is PlayerInputPacket ?

EDIT:
so PlayerInputPacket is when player click on boat or mincart and it sends player to server
and SetEntityLinkPacket sends server to players right?

https://github.com/PocketMine/PocketMine-MP/commit/4d6785ec866e9878841b804f46bd45ac1973a536
Considering that only PlayerInputPacket::decode() is implemented, PocketMine does not expect to send PlayerInputPacket.
Considering taht only SetEntityLinkPacket::encode() is implemented, PocketMine only expects to send, not receive SetEntityLinkPacket.