You may go to your settings by right clicking on the comparator called 'Settings' displayed in the ninth slot of your hotbar.
Settings allow you to change some things according to your preferences. There are a total of 7 settings available for you to configure, these will be listed below.
By clicking on it, you may enable/disable player visibility. This means if you disable it, you will no longer see players in the lobby. Note that you will not see players in the tablist either.
By clicking on it, you may choose to allow or disallow other players to send you duel requests. When this setting is disabled, you are still able to send duel requests to players, but they will not be able to send you any.
By clicking on it, you may enable/disable scoreboard visibility. If you disable this setting, You will no longer be able to see the scoreboard.
By clicking on it, you may choose if you want to see messages when players kill other players in chat. Note that you will not be able to see your own kill messages in the chat but other players will.
By clicking on it, you may choose if you want other players to be able to send you private messages through the /msg, /reply, and /r commands. This setting does not affect party chat. Players will still be able to send messages in parties. Find more information about player parties in the dedicated section. This setting does not affect friend messages either. Your friends will still be able to send you friend messages.
By left-clicking on it, you may set the time to Day; by right-clicking, you may set the time to Night. This is only client-side, meaning other players will not see the time as the one you set.
By clicking on it, you may toggle the chat. By turning this off, you will no longer be able to see messages in chat nor send any messages in chat. It is only client-side of course. You will, however, be able to send private messages to players by using /msg, /r, and /reply. You will also be able to send messages to your friends with /fmsg, /freply, and /frep.
NOTE: Needless to say, each setting will enable/disable a different feature, though your overall performance may be improved by enabling and disabling the proper settings. Make sure to set them up in the way that works for you!