Source code editors are the programs that allow for code creation and editing. Any text editor can be used to write code. But dedicated code editors offer many useful features, including: text completion, markup coloring, and tabs/panes for side-by-side editing. These features can be useful even to new users who don’t know their way around all of the advanced options.
There are many, many editors availble to download or use online, both paid and free. They offer many of the same core-features, but each have their own subtlties. Further research may help find the one that’s right for you. The following editors are all cross-platform and free to use or evaluate.
Sublime Text is a very popular editor that has been around since 2008. There are many options and extensions available, and a lot of help available online to help set it up. (The license for continued use costs $70. However, Sublime Text is free to download and evaluate, with a nag-screen pop-up.)
Brackets is a relatively new open-source editor by Adobe. It is very user friendly, especially for people who aren’t used to command-line interfaces or JSON-style settings/prefereces. Extensions and themes are quick and easy to find and install through the Extension Manager.
Atom is an open source editor, developed by GitHub. Like Sublime Text, Atom is quite popular. It is very configurable (“hackable”, as they say) but advanced features may be overwhelming to new users. There is also plenty of helpful documentation availble online.