RCU Forums - building from scratch question

Hi everybody Im new here and have been reading a lot on here the past few weeks.
Ive just got into RC boating for about a month now.
I want to build an electric RC boat totally from scratch.
I have been researching on youtube and on here and a few other sites but I am still not 100% how to do this.

I plan on building a 2 motor brushless system.
I want the boat to go at least 35mph (the faster the better)

So far i know I will need:
I plan on making my own fiberglass hull
2 brushless motors
I want to use (2) 7.2v batteries, 1 for each motor
2 shafts
2 propellers
an ESC
water cooling system for the 2 motors
Servo
rudder
controller

so my questions are:
what is the purpose of an ESC, What does it do?
what does a servo do, and where does it get hooked up to?
is the ESC the component that reads the frequency from the controller when I press up/down/left/right?
what other parts will I need?

if you cant answer my questions can somebody point me into the right direction for these answers please?
Im all about reading and watching videos to learn how to do this, I have just no clue where to start.
I want to buy all the components and build this boat from scratch.