Point A is where the Sun starts Hydrogen fusion
Point B is where about half of the supply of the hydrogen in the core has been used up. This is where the Sun is in its lifetime right now.
Point C is reached when there is no more hydrogen in the core and the fusion of hydrogen starts in the shell around the core. The radius of the Sun will swell to 40% larger than its present size and twice its present luminosity.
At point D, approximately one and a half billion years later, the surface of the Sun will be 3.3 times the size it is now and have a temperature of about 4300 degrees. The temperature on Earth will increase by 100 degrees, causing all the seas to evaporate and destroying life on Earth as we know it. Within another 250 million years, the Sun will grow 100 times larger than it is now and 500 times more luminous.
At point E the core temperature of the Sun will rise so high that in one bang, all the rest of the helium will fuse into carbon, causing one third of the solar envelope to be thrown out into space.