Hello Ricecakes.

What you are describing is the Private Browsing mode which is not a program that is separate from Firefox but rather a way to browse the web without leaving as many traces and without keeping a browsing history. You can read more on this here.

To not use this mode you simply have to open a new window (Shortcut: Ctrl+N). Make sure, however, that you do not open another private browsing window.

If you have any further questions about this feel free to ask.

You can check if you currently are running Firefox in permanent Private Browsing mode (Always use Private Browsing mode; Never Remember History).

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history

• Options/Preferences -> Privacy & Security
  Firefox will: "Use custom settings for history"
• remove checkmark: [ ] "Always use Private Browsing mode"