Assets and other content are reflected through formatted strings, each of which points to an online file or a file saved to the client's device. The basic structure is a protocol followed by :// and a string that varies according to the protocol.
|rbxassetid||An existing asset ID||Fetches a user-created asset uploaded to Roblox.||rbxassetid://7229442422|
|rbxasset||A file path||Fetches a file from Roblox's content folders.||rbxasset://textures/face.png|
|rbxthumb||Parameters and values||Allows for easy loading of thumbnails.||rbxthumb://type=Asset&id=24813339&w=150&h=150|
|rbxhttp||A path on the Roblox website||Fetches content from the Roblox website.||rbxhttp://Thumbs/Avatar.ashx?x=100&y=100&format=png|
|https/http||A website URL||Fetches content from a website using a URL.||https://www.roblox.com/asset/?id=9723979220|
For further guidance on using content, see Asset Format Strings.