There are several brands that are often put onto beginners' violins. Some of them work very well, others do not. These are my recommendations from my years of experience in teaching and playing violin. There are links where you can buy these strings online, and I earn a small commission if you do decide to buy here.
Sound: Bright, Loud, Somewhat Harsh
The brand I see the most on beginner's instruments is "Red Label". I recommend these, but understand that the sound on these tends to be harsh. You may be better off with one of the other brands listed below.
These have a bright, brassy sound, meaning it would be easier for a beginner to play loudly. These strings come in a variety of fractional sizes, meaning if you have a 3/4 or 1/2 size violin then you will be able to find strings for it.
The sound on these strings can get a little harsh. They tend to make sound even if you don't bow very hard.
They're made from a steel core wound with nickel. They tend to be easy to tune and keep in tune (unlike gut wound strings, for example).
Be sure to select the correct size for your violin!
Sound: Loud, Slighty Mellow
These strings tend to be slightly less harsh sounding, but they're still good for beginners. They stay in tune well, have a quick response to bowing, and are bright enough to project (play loudly and still sound decent).
These are also made with a steel core wrapped with nickel. This makes them stable (meaning they don't go out of tune a lot) and easy to tune.
Sound: Medium to Loud, Mellow
Price: Slightly expensive
Dominants are the mainstay of most violinists for their first several years. They project (play loudly well) quite a bit, but still have a good sweet sound, especially in the lower strings.
These are especially good strings if other cheaper strings are far too harsh sounding on your violin. They tune up well and stay in tune well.
These strings have a nylon core (called Perlon).This is what gives them their characteristic warm sound. Be aware that these strings will need to be replaced more often than steel core strings. (Between 6 months to a year, depending on use).
If you choose to purchase from the link below, I get a small commission. These are the strings that I use on both my violin and my viola. If you choose to purchase strings, please be sure you're getting the correct size for your violin, especially if you are a parent buying strings for a child's violin.
There are many different kinds of strings. These are just a few that I would recommend for those just getting into violin. You will often find that the strings on any rental instrument you get will need replacing very soon.
In general, you will want "ball end" strings. These are the most common. This means that on the end of each string is a ball, rather than a loop. The picture below shows ball end strings. They're not always gold and purple and the thread wrapping (the purple part below) is not always the same color.
Replacing strings can be a challenge. You can either bring your violin to a music shop and ask the people there to do it or see this page on how to replace a violin string.