what does it mean to be blocked? someone trolled and they were blocked but not banned? what does it mean?
Mostly blocked from editing the OSM database itself – someone more experienced might explain it better than I can
Blocked from editing OSM. These blocks can last for a set period of time or no time at all (in which case they are lifted as soon as the recipient has read the message they received with the block).
If someone continues to cause problems then they could face another block which could last longer. A multi year block is effectively the same as being banned.
It is also possible for users to be blocked on one of OSM related service, for example on this forums.
The most important role of a 0-duration block is that it blocks any API-only editing and forces the user to open their browser to the OpenStreetMap website and read the block message.
The forum software calls these either “suspensions” (no login) or “silences” (no posting except DMs with @/moderators).
…and they are visible on this site, along with the reasoning behind the block: User blocks | OpenStreetMap