Can You Explain Bass Strings?
There are a lot of different types of bass strings. Beginners may find this confusing. To understand the different types of strings, it's important to have a general understanding of a string's basic construction.
Each bass string has a core string around which another string is wrapped (or wound). On one end there is a ball or little metal ring to help hold it in place in the bridge. On the other end, where it attaches to the tuning post, the string is a little thinner which allows you to get more wraps around the tuning post.
Bass String Windings
Roundwound, flatwound, groundwound, and halfwound describe the winding on the string. If you look closely at your strings you will see little grooves all up and down them. Those grooves come from a little string that is tightly wound in a spiral all the way up the core string. A roundwound string has a round-shaped string wound on it. Picture a long string of spaghetti. A flatwound string has a flat-shaped string wound on it. It looks like a piece of linguine or a ribbon. (I must be hungry while writing this.) Since the flat string is wider, there are fewer grooves on the string giving them a real smooth feel. Less common windings exist, too. Halfwound and groundwound strings are somewhere in-between round and flat. Halfwound strings use an oval-shaped winding. Groundwounds use a roundwound string that is later ground down to have a smoother feel.
Which winding should you get?
Most people play roundwound strings. They have a nice bright tone and sound good for all sorts of styles. Other people like flats because they have a more muted sound to them. Flats also last longer and people like the smooth feel. The most important thing with strings is the tone. When people are listening to you they aren't considering how silky smooth the strings feel under your fingers or how often you change your strings. I would recommend getting roundwound strings unless you want to experiment. Flats always sound too dull to me. If you can, try them all out.
Bass Scale - (Oh No! Not More Scales!)
These are pretty painless. Scale refers to the length between the bridge and the nut of your bass. The standard scale is 34". Some 5-string basses have a 35" scale to get a better sound out of the low-B string. The standard bass size (probably your bass) requires long scale strings. Some smaller, shorter scale basses, like the Hofner Beatle Bass or Fender Mustang, require short scale strings.
Bass String Gauges
String gauge refers to the thickness of the string. The E-string is often .090" to .110" thick. Most often they leave the decimal off just saying 110 or 90, etc. The bigger the number, the heavier the string. Every manufacturer has their own way of naming string gauges medium, medium light, light, super light. There is a trade off between lighter and heavier string gauges. Lighter strings are easier to play and have a very bright sound, but are prone to breaking and lack a full tone. Heavier strings have a full tone, but require a little more effort to pluck and fret. Usually you should stick to medium gauge strings (105 - 45). The only time I recommend light gauge strings is if a person's fingers are real weak or if you are doing a lot of slap bass.
I hope this answers most of your questions about strings. You most likely want to buy a set of medium gauge (105 - 45), long scale, roundwound strings. Good luck!
Follow this link to see how to change bass strings correctly.