The second attack is a bonus action, not another Attack action. It counts as two attacks in that you have to roll the d20 twice, but this is a case where a term from a previous D&D edition might trick you in this edition. Let’s break this down into details.
Do you get multi attack on a held action?
A creature that can make multiple attacks on its turn has the Multiattack ability. A creature can’t use Multiattack when making an opportunity attack, which must be a single melee attack.
Can you attack multiple targets in 5e?
With the Extra Attack feature you can make two attacks when you take the Attack action. This does not force you to roll them simultaneously, you take one then the next. Rolling multiple attacks at once is for convenience to speed up combat.
How many attacks can a fighter make?
Fighters gain the ability to gain two or three additional attacks at higher levels, so a 20th level fighter is able to make 4 attacks when they take the Attack action. Two-Weapon Fighting can only be used when you take the Attack action. You may use your bonus action to attack with your off-hand weapon.
Can you hold multiple attacks?
No. Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn. The Ready action lets you take the Attack action on someone else’s turn, and thus extra attack does not apply.
Can you split Multiattack?
Technically no, because the multiattack is an entire single action.
Can Multiattack hit more than one target?
If you have the ability to make multiple attacks in a round, they can be against the same target or another target unless the specific ability prohibits it. You can move between attacks, as mentioned on page 190 of the PHB.
How many attacks does a fighter get at level 5?
When you are a 5th-level fighter and you take the Attack action, you can make two attacks. You can also use your bonus action to make an additional attack. You only add your ability modifier to the damage of that bonus-action attack if you have the Two-Weapon Fighting fighting style (PHB, page 72):
