tl;dr: Run vimtutor, learn vim, enjoy life

It's extremely powerful, for mostly the same reason that it's incomprehensible to newbies. It's focused not on directly inputting characters from your keyboard, but on issuing commands to the editor on how to modify the text.

These commands are simple but combine to let you do exactly what you want with just a few keypresses.

For example:

w is a movement command that moves one word forward.

You can put a number in front of any command to repeat it that many times, so 3w moves three words forward.

d is the delete command. You combine it with a movement command that tells it what to delete. So dw deletes one word and d3w deletes the next three words.

f is the find movement command. You press it and then a character to move to the first instance of that character. So f. will move to the end of the current sentence, where the period is.

Now, knowing only this, if you wanted to delete the next two sentences, you could do that by pressing d2f.

Hopefully I gave a taste of how incredibly powerful, flexible, yet simple this system is. You only need to know a handful of commands to use vim more effectively than you ever could most other editors. And there are enough clever features that any time you think "I wish there was a better way to do this" there most certainly is (as well as a nice description of how).

It also comes with a guide to help you get over the initial learning curve, run vimtutor in a console near you to get started on the path to ~~salvation~~ efficient editing.