Censorship Risk
The risk that certain transactions are excluded or delayed because the parties who order transactions choose, or are required, to leave them out.
Inclusion is decided by whoever builds blocks, and on networks with specialized builders and relays a small number of firms may construct most blocks. Those firms are legal entities in real jurisdictions, so they may filter transactions touching sanctioned addresses, which is compliance from one side and censorship from the other. Filtering at the ordering layer is usually partial, producing delay rather than permanent exclusion, as long as some producers do not filter. Additional chokepoints sit above the chain: hosted endpoints wallets query, front-end websites, and, for rollups, a single sequencer, which is why designs include forced-inclusion mechanisms and inclusion lists that let users route around a filtering operator.
In practice
Rollups typically provide a way to submit a transaction directly to the underlying chain if the sequencer refuses it, so a user is delayed rather than permanently excluded.
The common misunderstanding
That censorship on a public blockchain means transactions are blocked forever, when it usually means delay and reliance on the minority of producers that do not filter.