Definition
An AI that helps a person complete tasks (drafting, scheduling, summarizing, researching) and is typically reactive: it responds to what you ask rather than taking initiative on its own. It works turn by turn inside a chat window or an app, holding context for the conversation but not owning a job from start to finish.
What it looks like in practice
At a two-attorney family law practice, the assistant works like a very fast paralegal who never files anything. The office manager pastes in a long client email and asks for a summary and the three questions that still need answering. She has it draft a retainer follow-up in the firm's usual tone, then rewrite it warmer. Before a Thursday hearing she asks it to turn six pages of notes into a one-page chronology. Every one of those saved her real typing time, and every one started because she opened the window and asked. Nothing happened on Wednesday, because nobody prompted it.
Why it matters
For most owners this is the first AI that earns its keep, nothing to set up: open it, ask, get something usable. The line worth understanding is the one between an assistant and an agent. An assistant waits for you and works one turn at a time. You hold the plan, it does the typing. An agent holds the plan itself, takes several steps unprompted, and reports back. If the bottleneck is your own drafting and thinking, an assistant helps immediately. If the bottleneck is work nobody has time to start (the follow-ups nobody sends) an assistant won't touch it; a managed service or an agent is what you need.