The plugin (srcexpl.vim) is a source code explorer based on tags and it provides an overview of the function and type definitions.It has such a mechannism that works like the context window component of "Source Insight" software.
If you have used Source Insight for browseing C/C++/Java project before, you may find that you can browse the definitions with the Source Explorer as well as the context window of "Source Insight".
For example, you put the cursor on a function name in the Normal mode, its definition will show on the Source Explorer window a moment later. As soon as you do the 'double-click' operation using your mouse onto the Source Explorer window which had appeared on the bottom of (G)Vim, the definition and its context will be shown on the editor window.(Just like Source Insight does). Besides, multi-definitions' listing and jumping works like the Source Insight too. In srcexpl v1.2 and above, the function key which users mapped will play a important role that you can not only use mouse but also use keyboard in order to exploring source code in both GUI and cterm VIM.