Some characters and androids are allowed a second action. This is because they're either faster than normal humans or have augmented reactions. These characters have access to the Second Pedestrian Phase. No other character has, and thus if a game involves no augmented characters or fast androids, then this second phase won't be needed.
If a character has a second action, then it must be taken in the Second Pedestrian Phase. This phase comes just before the second vehicle phase. A characters first action must always be taken in the first pedestrian phase. A character is never allowed to take all their actions in one phase.
If a character has a movement of more than 8 cm, then they must have a second move action - the remaining movement after 8 cm being their second action.
A character will have a second move action if they have a speed of more than 8 cm. To be able to use that second move action, they must move their full 8 cm in the first phase. They will then be able to move the remainder of their movement in the second phase. Note that the first 8 cm must be spent in the first phase. It cannot be split up to allow a greater second movement, and if a character moves less than 8 cm, then they are not entitled to use their second action.
In addition, if this is just a move action, then it may not be combined with a shoot action.
If a character has a non-move second action, then they may use it however they wish, with the proviso that it does not include moving. It can be a shoot, close combat or other action though.
Sometimes a character or android may have a second move and another non-move action. If this is the case, then these actions may be combined to create a move and shoot action, and if the character moves and shoots, then this is automatically assumed to be the case.
When you're using a lot of pedestrians with cyberware and/or androids, then you might find the second pedestrian phase slows things down a bit. If this is so, then you may find it quicker to make all pedestrians take their second actions at the same time as their first, thus ignoring the second pedestrian phase in the whole place.