Git tracks and manages changes, not files。Git can only track changes to text files, such as TXT files, web pages, all program codes, etc. For example, the word "Linux" is added in line 5 and the word "Windows" is deleted in line 8. Although the binary files such as images and videos can also be managed by the version control system, they cannot track the changes of the files. They can only string together the changes of the binary files each time, that is, they only know that the image has changed from 100KB to 120KB, but the version control system does not know or can not know what has changed.
It should be noted that if you submit in the following manner:
First modification->add->Second modification->commit
Then, the second modification will not be submitted.
If submitted in the following way, both modifications will be submitted
First modification->add->Second modification->add->commit
Therefore, content without add will not be submitted even after commit.