Google drive comes with every @Gmail adress, and has a set amount of free storage. This storage can be used for a variety of things, such as spreadsheets, document editing, and storing of files. The easy part is that all this is done online, in your browser. That means that no matter where you log in, you can see and edit your files. The downside, you need to have an active internet connection for this.
You can create new files in Google Drive using the large New button. Select the type of file you wish to create, and a new Untitled document will be created.
By simply double clicking on a file in Google Drive, you can open the file. Right clicking on a file will open the context menu, showing you the different options that you can perform on a file. These actions are for example deleting a file, or sharing it with others.
Sharing a file requires very little effort. In your Drive, right click the file and select the share option. Enter the email address of the other person, and they will receive a link to your file. You can even get a shareable link, to send to others. This is for example useful if the other person does not have a google account.