The two screenshots can probably explain gmail drive better than I could. Gmail drive is a shell extension that allows you to use your gmail account as a storage medium.
This is an excellent tool for file backup, but I also use it to upload files that I want to email to other people.
I think the upload speed for gmail drive is much faster than the upload speed you would get from using gmail in a regular browser.
The pros: This is tool is convenient and very organized.
The cons: Unfortunately, the file size names have to be less than 65 characters, and this tool is still considered experimental. It is possible that google may try to disable this tool in the future.
Download the tool or visit the gmail drive site for more information.