dd5e – Please clarify Multiple Attacks and attack Advantage?

Any time you get advantage on target you roll 2 dice and keep the better roll the opposite for Disadvantage, I get that. How does this effect attacks if you have multiple attacks like from fighters/rangers/monks/warlocks (thirsting blade, eldritch blast), sorcerers (quicken, twin metamagic attack spells), etc? Is advantage only reserved for the initial attack and not any after that?