Anyone that has been to Bolivia and eaten in a restaurant / cafe or two will no doubt have been served with the meal from time to time a small bowl spicy tomato based sauce. Some love this immediately others will find it more of an acquired taste.
This sauce is called "llajua" (sometimes spelt differently with "llajwa" also being a common form) and pronounced "yak-hwah". It is a simple sauce made from tomatoes, locoto chilli peppers and often has either kilkiña or wakataya herbs added to it which are locally grown herbs that offer a unique taste.
The spiceness of the sauce can vary greatly depending on the hotness of the chillis used and of course the quantity. The amount of the herbs used can vary a lot ranging from a small amount to add a hint of flavor to some sauces been green in color due to containing large amounts.
The name llajua is a traditional name but the Bolivian Government actually managed to trademark it in 2008. There are some similar sauces available in other nearby Andean regions but usually not exactly the same although the closer to Bolivia the more similar it could be.
Most Bolivians love this sauce (not all of course as some simply dont like spicey food) and this accounts for the fact that just about every street food stall , local cafe or restaurant and a large amount of higher standard restaurants serve this without even asking. It is regularly provided as a pre-appetizer with bread as a dip, served in fast food joints on the fries and used to add a bit of kick to the sometimes bland traditional main courses.
If you are visiting Bolivia you should certainly give it a try and you might come to love it like the locals. Unfortunately the herbs used to make it are not available elsewhere in the world so if you do get a taste for it you will likely miss it when you return home.