Installation is straightforward and it should be in your distro’s software manager. Just use the search facility. It took just a few seconds to add to Linux Mint for instance.
Geany has a three pane display and on the left is a panel with tabs for Symbols and Documents. The main window shows the text or code and multiple files can be opened on tabs. At the bottom is a multifunction panel that can show messages such as status, there is a scratch pad for storing bits of text, and a mini Terminal window.
On the left, the Documents tab shows the files that are open. The Symbols tab shows different information depending on the type of file open. It might show headings, such as H1 and H2 tags in an HTML file, classes, IDs, and other definitions in a CSS file and so on. It is basically an aid to navigation in whatever file is open.
There is support for a wide range of file types, too many to list here, and it can edit almost any you are likely to come across when writing text or programming code. The way that it automatically colours the code is excellent and it makes functions, parameters and other items really stand out.
It can fold code to make editing and navigation easier. For example, it automatically recognises <div> tags in HTML, function definitions in other languages and so on. Click the little symbol next to the opening tag, function or definition, and it collapses the code and hides everything up to the closing tag or end of the function or definition.
Lines can be automatically wrapped in the editor, automatically indented, you can strip trailing spaces, set line endings to Windows, Unix or Mac, replace tabs by spaces and spaces by tabs, and much more. New files can be created using templates for HTML, PHP, Java, Python and other popular languages.
Geany has an impressive range of features for such a small program. If you do any type of code editing it is well worth installing.