An SME is someone a team turns to when a subject needs more than a general answer. The term stands for "subject matter expert", which usually means someone who knows a particular area well enough to explain how it works and point out the details or exceptions that matter.
That expertise is not always technical in the usual sense. An SME might be the person who understands a product workflow or a reporting process. In other cases, they may be the one who knows an internal system that only a few people use regularly, or the person a team relies on for compliance or integration questions. What matters is that they hold working knowledge other people need when they are trying to make a decision or get unstuck.
In practice, an SME is often involved when a team needs clarification. They may review a document or step into a meeting to answer questions. They are not always the person doing the work themselves. Sometimes their role is simply to help other people understand the work well enough to handle it correctly.
SME in Context
You may hear this term during planning, review meetings, or in project handoffs, especially when a team needs help untangling a process. If someone says, "We should check with the SME", they usually mean, "We need input from the person who knows this area best".
That can be useful for non-technical professionals, because it gives you a clearer sense of where reliable information is likely to come from. If a process feels confusing, or you need clarification and accurate answers, the SME is often the person who can fill in the missing context.