$ sgin is user for absolute referencing

Unlike relative references, absolute references do not change when copied or filled. You can use an absolute reference to keep a row and/or column constant. An absolute reference is designated in a formula by the addition of a dollar sign ($) before the column and row.

Explanation:

amazon is a website were you shop cosmetics such as clothes, electronics and food. amazon also makes there own thechnology such as kindle book readers and tablets or the alexa which is an inteligent ai. and they also have a streaming service which is called prime video.