Question - What is the propose of getSharedDependencies?

Just wanted to clarify the following similar doubts.

1. What is the propose of getSharedDependencies?
2. Can we add all the packages that are being used in the host and mfes level in the `dependencies.json` file?
1. Does it impact the app bundle size?
2. Or do need to follow any pattern to specify the dependencies in the `dependencies.json` file?
3. If we specify a dependency in `dependencies.json` file and host package.json file then can we use that dependency in all the mfes without specifying in the respective mfe package.json file?