What is the difference between Tor, Tor Browser and torbrowser-launcher?

Tor, sometimes called little-t-tor, is the core of the Tor Project's software. It acts as a SOCKS proxy and anonymizes your connection. You can set up Tor in your torrc. This file is either in the directory /etc/tor when Tor is installed as a system-wide daemon or it is in your local home directory when you use the Tor Browser.

Tor Browser is a browser (like Firefox) which comes with Tor and some other software. This software enables you to safely access the web in a secure way. You can change settings by pressing the green onion inside Tor Browser or by entering about:config into the URL bar.

The torbrowser-launcher is a software which starts your Tor Browser. It checks if a new version is available, downloads if there is any and starts the Tor Browser. It only has one parameter (--settings) which opens a settings dialogue.