You should always take caution when opening attachments from emails. Attachments themselves are not necessarily harmful, they’re a great convenient way to share pictures or documents using the Internet. Most email programs will indicate that an email has a message with a paperclip icon. By default, Gmail shows an icon with a filetype.
So how can attachments be dangerous?
Email attachments can be harmless and useful or they can be malicious and designed to harm your computer. Generally, if you are expecting an attachment or it’s from someone you know and looks like an email they might normally send, it is safe to open the attachment. You should never open attachments that you were not expecting and should delete them without opening the email period.