a walking foot (or sometimes called an even-feed foot) is used for stitch in the ditch or other straight line quilting
a darning foot (sometimes called a free-motion- or hopping foot) is used for free motion quilting-
the walking foot works with your feed dogs to evenly feed the fabric top and bottom through the machine-
the darning/hopping foot is round- you use it with the feed dogs lowered- it (hops) and you can move the fabric in all directions(because the feed dogs are not feeding the fabric- you have to do all of the moving)
you can use a regular foot for straight line quilting- good basting is a must- and if it is possible to (ease) the foot tension that will help you - the main problem with using a regular foot instead of a quilting foot is the *bulk* of the quilt sandwich- you tend to get puckers along the stitching line- one way to 'ease' that problem is to lengthen your stitch length- or lessen the pressure of the foot.
there are many many tutorials and videos showing the techniques- you may want to check some out- then put together some practice (sandwiches) and try it out- some people make 12" squares to practice- then make potholders or something with their practice pieces.