Remote Event is one-way-connection Client-Server / Server-Client

Remote Function is two-way-connection Client-Server-return back to Client / Server-Client return back to server

examples:

So Simply if you use a remote event you fire it like this:

remote:Fire(stuff) | remote.OnServer/ClientEvent:Connect(function(stuff) print(hi) end)

the remote will print hi

but on the other side Remote functions work like this:

local ret = remote:Invoke(stuff) print(ret) | remote.OnServer/ClientInvoke = function(stuff) print(hi) return "hi" end

the remote will print hi 2X (twice) because of the first print and the return

click the source for more info.