Sharing a document, presentation or other file allows others to see or edit the file which you have shared with them. They can access the shared file by going to their Google Drive and clicking the "Shared" folder on the left hand side.
In the text box type in the email of the person you want to share the document/presention/file with. To the right of the text box is a drop down menu where you can choose if this person is able to "edit," "comment," or "view."
Can Edit: gives the person full acess to change and/or add material to your document/presentation/file.
Can Comment: allows the person to leave comments about your document/presentation/file on the right hand side. (Commenting will be covered in the Collaborative Work tab)
Can View: only allows the person to see your document/presentation/file they can not comment on or change anything within the file.
Click the button on the upper right hand side of the screen while in the document you want to share.
Once you click the button this screen will appear.