Following the 1st pull and you’ve nailed the hang position it’s time to generate as much force as you can, in a controlled manner, to propel the bar in a vertical motion so you’ll be able to pull yourself under and receive it overhead.
The second pull is often referred to as a jump, however, it’s important to mention that one is not supposed to actually jump. The 2nd pull is very similar to jumping mechanics, however, there is a difference. A jump can only be qualified as a jump when the centre of mass exceeds the point in which a lifter is not any longer touching the ground after fully extending at the hip, knee, and ankle and the WHOLE body is in the air. During the second pull, the lifter will achieve triple extension, but will not achieve any further displacement after the pinnacle of the extension, meaning the feet still have contact to the floor. From here the lifter will change direction towards the floor again to receive the bar overhead.
It’s often a big fear factor for beginners to achieve full triple extension since the bar has to make contact at the hip to be continue its upward motion. The fear factor is considerably worse for male lifters since their "trouser snake" is in close proximity when the bar contacts the hip (Slightly above the pubic bone). The hip contact varies between the different lifting styles, where the Asian population has more of a swift/smooth contact, and the eastern European countries often have a harder contact. I’d encourage people to go more towards the smoother style since it won’t shoot the bar forwards as much as the harder contact style will. This is where the velocity achieved from the 1st pull comes into the picture, since it’s easier to make the triple extension smoother if posterior trunk lean occurs straight after the hang position, this is obviously only if the 1st pull and hang position have been optimally obtained.