remote function or remote events. when to use which one?

Say you wanted to get a value of the client while using FE, you would make a script like:

-- Server Script
rf = Instance.new("RemoteFunction", workspace)
rf.Name = "GetPlayerName"
-- Client Script
rf = workspace:WaitForChild("GetPlayerName")
rf.OnClientInvoke = function() -- Callback function
	return game.Players.LocalPlayer.Name
end
-- Other Server Script
print(workspace.GetPlayerName:InvokeClient(game.Players.SebbyTheGODKid))

That will print "SebbyTheGODKid"

But say you JUST wanted to use a remote event to place a block from the client:

-- Server Script
re = Instance.new("RemoteEvent", workspace)
re.Name = "PlaceBlock"
re.OnServerEvent:Connect(function(pos)
	if pos ~= nil then
		part = Instance.new("Part", workspace)
		part.Position = pos
	end
end)
-- Client Script
workspace.PlaceBlock:FireServer() -- Returns nothing, but places a block on the server even with FE.

Hope that helps!