Once you have created and sent a quotation to your customer, s/he will receive an email.
There will be a link in the email clicking which, your customer will be able to view the details online and be able to Accept/ Reject/ Comment about the quote received.
Whatever and whenever an action is taken by the customer on the quote received, it will be updated on your quotation detail page.
If the customer has any questions about the quotation received, s/he can add them to the Comment (Notes). These notes are visible to both you and your customer. Not only this, you can respond and communicate with your customer through Notes in Quotation Detail page instead of emailing separately.
This is how Comment/ Note feature will look like when used:
Customer's Quotation Detail Page
Your's Quotation Detail Page
Accepting the Quotation
Once your customer has accepted the quotation sent, you can Convert it to the Invoice.