There are many ways to carry your money and papers with you on the road - and a neck wallet is a popular one. It allows you to literally 'hang' on to your belongings and is relatively comfortable, as far as these things go.
A typical one is made up of two parts: a cord-like length that hangs around your neck, and a pocket or pouch, which you wear under your blouse or T-shirt.
One advantage is easy access - it's much easier to dip into one of these pouches than into a travel money belt around your waist. You also don't have to half undress to get into it.
On the other hand, it's easier to spot - and to steal although you can also find zippered neck wallets, which some people prefer.
There are ways around its vulnerability too. Several manufacturers offer a slash-proof cord, which keeps the wallet lightweight but is a tough combination of wire and cotton or polyester. Even so, don't be tempted to wear it outside your clothes. Even if it's sturdy, you're still calling attention to yourself and that is something you want to avoid.
The neck pouch itself tends to be large enough to carry your passports and precious papers, as well as a few other valuables, such as a ring. (I don't recommend taking any valuable jewelry - unless you are psychologically prepared to lose it during your trip.) There are even larger pouches that allow you to stash your smartphone.
Neck wallets are usually made of polyester or nylon lightweight material, with zippers or velcro to seal the pouch or pouches (some people have several). It isn't usually waterproof or sweatproof, so you'd have to put anything made of paper into a ziplock plastic bag first.
It you have a large chest, this might not be the ideal approach for you. It can stick out as it hangs, and can be slightly uncomfortable or chaff around your neck (if you pick the wrong model or size it can also get caught between your breasts so make sure it's the right length). I don't personally like the neck wallet because it tends to swing around under my clothes. But many women backpackers swear by it!
Street thieves often target women wearing so-called hidden pouches around their neck. The cord can be seen peeking out and sends a signal you are carrying valuables in a relatively accessible place. It's not uncommon to hear of pickpockets slicing the cord, giving it a tug and running off with the pouch. For this reason the leg wallet, which is completely hidden and grasps your lower calf with a wide elastic band, is becoming increasingly popular, and there's always the traditional standby, the travel money belt, which is worn around your waist.
They all serve the same purpose - to keep your belongings safe while you carry them, so just try them all on and choose the one that will make you feel the most at ease.