
What is a stravenka?
Stravenka (Czech: "stravenka") - Czech food voucher. In other words, this is such a voucher that can be spent in various eating places, including stores.
For better understanding I advise watching my video too:
What kinds of stravenky are there?
They come in all different kinds, they differ both by the company providing them and by denomination.
I have on hand only, perhaps, the most popular ones - from the "Sodexo" company:

As visible in the photo - consider this simply a banknote of 95 (like in Eldorado) crowns, which can be spent on a limited assortment of goods.
Where can they be spent and on what?
You can spend stravenky only on food. They're accepted by the absolute majority of cafes, restaurants, and also stores with products. If you didn't see a sign anywhere, before ordering\buying it's worth asking whether the establishment accepts stravenky.
How to get stravenky?
In theory, you can get them in different ways. The most obvious is receiving them at work. I'll note, however, that not all employers do this.
It works like this - the employer establishes how many stravenky per day\month they'll give you (for me, for example, the system is this - for every 8 hours worked - 1 stravenka). Then, before calculating your salary they'll deduct a certain amount from you. In my case it's calculated like this - you pay 45%, employer - 55% of its cost. Percentages change from employer to employer.
Thus it's easy to guess that for each stravenka with denomination of 100 crowns they'll deduct 45 crowns from your salary, the remaining 55 the employer will pay.
At the beginning of the month they'll give you an unsealed envelope with stravenky, which can be immediately spent.

Advantages
Actually, despite the fact that this is just a food voucher, just like under socialism, it carries a lot of good with it.
- The worker significantly saves on food (and, in principle, 100 crowns in Czech Republic is enough for 1 good lunch per day)
- The stravenka price is simply deducted from salary, you don't need to pay taxes for them
- Any person who came to Czech Republic notices the high level of public catering establishments (as, for example, in Poděbrady cafes) - stravenky simply stimulate people to have lunch in public eateries. Cafes, in turn, in conditions of high competition try to improve service quality
Minuses
- You can't buy beer (and alcohol in general) with stravenky
- Stravenky are produced by ordinary private companies. Why some separate firms get perks from the fact that all people eat - is unclear to many
As far as I remember, scholarship recipients in Poděbrady were given part of the scholarship in the form of stravenky - many didn't spend them all, sold them for half price. Dealers - they're dealers in everything.