You share a form if you want your colleagues to collaborate on the creation of the form. If you share this form you need to understand they will have edit and copy rights to your form. You share a form the same you you share other Google Drive documents.
Sending a form is the method you use if you want people to take the survey and answer the questions on the form. Sending a Google Form is really easy. Simply click the "Send" button in the upper right hand corner and post the link in classroom.