The two heads you are most likely to encounter are easy change heads and bump heads, it’s important to note that Victa petrol models come with both.
Easy Change Heads
A simple disc with a series of holes through them and a hook in the middle. Line is cut to size, or bought pre-cut, and is threaded through the head so an equal amount extends from each side. As the line wears down the stump of line needs to be removed and a new piece inserted.
Contain a self-feeding mechanism. They have a large amount of trimmer line wound on a spool within the head itself. As the line is worn down you simply bump the head on the ground to release extra trimmer line. This means there is less time replacing line into the head allowing you to trim for longer without interruption.