How does VFR work in countries other than USA? What does hi and lo mean?
The "hi" and "lo" represent en-route high altitude and en-route low altitude.  The difference between the two is the transition altitude when switching from flying with reference to height to referencing altitude

The transition altitude varies from country to country (e.g. typically 18000 for the US and 3000 in the UK unless varied - 6000 in the London area for example) and can be found in various publications and on the en-route charts themselves.

The structure of airspace is consistent world-wide with some variations which are always marked on the relevant charts. There are far too many small variations to go into any detail here.

Finally, the charts themselves. Because the structure is consistent, the charts are also consistent although there are cosmetic differences such as the symbols used, colours used and certain pieces of useful information which may or may not be printed upon them.  The differences are easy enough to  learn quickly.  I've flown VFR in the  UK and the US and the charts look different, but are fundamentally the same. Within an individual country, charts may even differ cosmetically if the airspace is particularly busy when the chart makers may choose to omit less important information.