vim change cursor in insert mode code example

Example 1: vim insert after cursor

a - insert (append) after the cursor

i - insert before the cursor

I - insert at the beginning of the line

A - insert (append) at the end of the line

o - append (open) a new line below the current line

O - append (open) a new line above the current line

ea - insert (append) at the end of the word

Example 2: vim replace under cursor

Just use * and then:

:%s//new value/