The Main Menu gives you access to many of the features of ELinks via submenus and serves as a good entry point for performing actions on the different objects of interest, such as links, documents and tabs. The Link menu and Tab menus are more specialized and targeted to a specific context, such as link handling or managing the tab bar. Actually, the Link Menu is accessible from the Main Menu as a submenu.
Once you have familiarized yourself with the menus, you will have a good chance at gradually learning the most common keybinding, since all the configured keybindings are shown as right aligned text. Menu entries can also be quickly accessed using hotkeys. Hotkeys appear highlighted in the menu entry text. For example the key-combo "Alt-v i" will open the document info dialog accessible from the View sub menu in the Main menu.