Parallel

Several things happening at the same time rather than one after another (which is serial). It's the plain word underneath the fancier ones: fan-out is one job split into many parallel copies, a swarm is many agents attacking one problem in parallel, and "run these three checks at once" is parallel too.

Three job sites running on a Tuesday, instead of one site for three weeks.

Why it matters: agents don't get tired and don't queue politely, so doing things at once is nearly free capacity — which changes the question you ask. Not "how long will this take?" but "what can't safely happen at the same time?" That second question is the real work, and it's a judgement call rather than a technical one.

Related: Fan-out · Multi-agent / swarm · Async (asynchronous)