You need a special card for your computer that converts AV signals so they can be recorded as movie files on your computer. You usually get basic video editing software bundled with it. They usually also have a TV receiver built in so you can record TV to computer.
Some digital camcorders can convert AV input to Firewire. Macs and an increasing number of PCs have Firewire inputs.
This is the sort of thing you need. It connects between your video source ( either VHS or analogue camcorder ) and a spare USB port on your computer. Comes supplied with software to convert your tapes to DVD. This will not work with copy protected VHS tapes.