The file extension is the last part of a file name.
What format the file has.
For example: pdf
A search engine is a website.
It searches the internet for specific information.
The equipment for filming includes, for example, camera, light and tripod.
Putting the video into a certain file format.
For example: mpg, .mp4, .mov
An eBook is a book in digital format.
It consists of text and images.
You can read it on a PC screen or other electronic device.