Buffs allow you to upgrade a drones ability set. Related, but slightly different, are Weapons.

Buffs are stackable, and they last until you die.

Shield (Buff)

Shield creates a shield similar in height to the drone, but not full height, in front of the drone - it glances attacks that connect with it before they connect with the drone itself, but will disappear for a short time after being hit before regenerating.

source: @Viotech3#8512 on Discord

Speed (Buff)

Speed : 20% buff to movement speed and cooldowns (although there are a few odd cases, such as a 30% cooldown reduction with gun).

Snail Speed by Map Without & With Speed Buff

Map No Speed in Seconds With Speed in Seconds
The Pod 26 ?
The Split Juniper 26 ?
The Spire 26 ?
Tally Fields 20 ?
Helix Temple 20 21 (solo)
Black Queens Keep 20 ?

source: @drainy#1038 on Discord

Buffed Warriors

It's possible to get these buffs on warriors, too. For example, you could have speed and sword at the same time. However, because warriors cannot carry berries, you must get the buffs before your weapon of choice. Note that in the case of the shield buff, the shield disappears when you are in the middle of an attack, making shield+mace almost completely useless.