If you forward any video clips or mp3 files from your mobile phone from any other contact it sends immediately in WhatsApp.
You may wonder that how is this possible or they have stored all media files on their server.
Whatsapp stores all files and attachments on their database with its own checksum. Every file can be represented by an alphanumeric sequence of characters in it.
When user uploads a file whose checksum is already present on their database, they just use the uploaded copy of the file stored on their server.
This has several advantages. It has several advantages which includes preventing double uploads, avoids server overloads, save your mobile data, whatsapp save space on their database.
Similar technique is also used by dropbox to transfer files.
Also, While sending images in WhatsApp, there is an option to add caption to it. This caption is visible on image, at the receiving end, but when this image is copied or forwarded, only image is received.
To resolve this issue, try following steps:
Select an image along with caption that you want to forward.
Choose "Arrow/Forward" Button. This will show "Select contact" screen.
Click 'OK' when asked about forwarding to selected contact.
This method should forward image from conversation/chat along with Image's caption to the recipient.