This will display help about the particular function that you are trying to use. For example, if you are using the Search and Replace function and press the F1 key (this is almost always the Help key), the software should display advice on how to use the search and replace function. If the software didn't have context-sensitive help it would just display a general manual and you would then have to look for the section on Search and Replace.
Almost all well-designed applications now have context-sensitive help. It isn't quite the same as bubble-help, which is a single line that describes what you are pointing at on the screen. If you're not sure what a particular button does, move the pointer over it and wait for a second or two. A little 'bubble' with a one-line description of what the button does will pop up. Not all software has bubble help.
There is another type of context-sensitive help called Cue Cards. These were originally developed by Microsoft, but lots of other software developers are now using a similar concept. When you use a function, there's a little window at the side of a screen that explains exactly what you're doing and tells you what you should do next. As soon as you are familiar with a program and know what you're doing you can switch off the Cue Cards.
