what does rebase mean in git code example

Example 1: git rebase

#The branches are like this
          A---B---C topic
         /
    D---E---F---G main
#git rebase <base> <target>
git rebase master topic
#<target> get moved forward on <base>
#NOTE: commits on <target> change their hash
                  A°--B°--C° topic
                 /
    D---E---F---G main

Example 2: what is git rebase

the rebase command integrates changes from one branch into
another. It is an alternative to the better known "merge" 
command. Most visibly, rebase differs from merge by rewriting
the commit history in order to produce a straight,
linear succession of commits.

Example 3: git rebase vs merge

Git rebase and merge both integrate changes from one branch into another. Where they differ is how it's done. Git rebase moves a feature branch into a master. Git merge adds a new commit, preserving the history

Example 4: git rebase

git rebase -i --root
git rebase -i HEAD~3