ResearchA Guide to Hooks, Lines, and Sinkers
Once, fishing line was made of cotton that had to be dried after each use to prevent its getting moldy. Today we've got nylon that is much stronger and doesn't absorb water, and besides that we have monofilaments, braids, gel-spun polyethylene, and dozens of other materials. We have different thicknesses and textures for different fishing and casting needs. Fishermen are very serious about their line.
Most fishermen are best-acquainted with monofilament fishing line. One simple, solid, and very long strand of plastic string. While there are better types of line for certain needs, monofilament is the most versatile and common. It's a little elastic, which over repeated uses can be a bad thing, but it gives you a few precious extra seconds to react when you feel something tugging before it breaks. Monofilament is available in different colors. Most fish are smarter than we give them credit for; if they see a prospective meal is attached to a mysterious length of string leading out of the water, they're not touching it. Select line with a color closest to that of the underwater ambient color of your fishing spot.
Hooks are an old invention; ancient fishers used to make them out of bone. Today, we make them of plated and galvanized metal. We also make them into many different shapes, corresponding to the different mouths of various fish. I will assume, with great confidence, that you don't want me to list every single shape of hook and expound on the nuances of each. Really, there isn't that much to say about them. You've got single hooks, double or two-sided hooks, and three-sided hooks. Use the single hooks, in various sizes, for small to medium fish; use the double and treble hooks for big ones. Ask the tackle shops' sales staff about what kind of hook is best for which situation, and they'll no doubt gladly chew your ear off about it.
Sinkers were invented when fishermen realized they had to, you know, get bait underwater in order for the whole wild scheme to work. Your typical sinker is a lump of lead shaped like a teardrop with an eyelet at the point, through which you loop and tie your line. There are sinkers which are shaped like hinged spheres with a recess through the center that clip directly onto the hook, for bottom trolling. Sinkers come in all kinds of sizes, since gravity applies underwater as well as above. They range from the size of aspirin to the size of fists. There are also floaters, used in fly fishing, which keep the hook from descending beyond a certain threshold and alert you by bobbing when you've got a bite. Your average fisherman requires a fairly narrow range of sinkers anywhere from an ounce up to a pound.
So now when somebody says "hook, line, and sinker", you found out about all three in one place. These are the basics, together with rods the least a beginning fisher needs to know.