several sheets; a few flat objects
Used for counting flat, thin items such as paper, tickets, plates, or photographs. The counter 枚 is for flat objects.
I submitted several sheets of documents.
写真を数枚撮った。
I took a few photos.
数枚 is used for a few flat objects like paper or plates, while 数個 is used for general countable objects.
Compound of 数 (several) and the counter 枚 (for flat objects).