Is there a simple text editor (like gedit) with options to make text bold?

If you want a text editor, there is no such a thing as bold.

Plain text is plain text. The bold, italic, colored thing you see in a programming editor like gedit, geany, kate, etc. is syntactic highlight, added by the editor to facilitate the reading and writing of programs or whatever --- it is not stored with the text.

Now, you can leverage this to see bold in the gedit. For example, if you save your file like a markdown (extension .md), you will see this:

...using the same syntax you use in Ask Ubuntu to make pretty questions and answers. You can then have a lot of tools to pretty print them, like for example pandoc.

Otherwise, you are looking for a word processor, which is another kind of beast completely. You have a partial list here; I heard very good reviews of Ted but never tried it.

If you want to look at source code with rich formatting, then Geany or Kate is your best choice.

However, it seems that you basically want a Rich Text Editor. In this case you should go for Abiword or Calligra Words.

Abiword is much like WordPad. Install Abiword:

sudo apt-get install abiword

Emacs is an easily customizable text editor which is widely used and probably has more features then any other open source text editor out there.

To install, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:

sudo apt-get install emacs

Once you highlight what you want to make bold, then: