Used to refer to a small, unspecified number of people, typically more than two but not many. Common in both spoken and written Japanese.
Several employees attended the meeting.
We received questions from a few people.
数名 means the same 'a few people' as 数人 but sounds more formal, often used in written notices or business contexts.
Compound of 数 (すう, 'several') and 名 (めい, counter for people). The counter 名 is a polite way to count people.