Source: Starfinder Core Rulebook p.114
The guard fighting style focuses on defense. You become adept at wearing armor, protecting against attacks, and enduring damage and other setbacks from attacks that get through your defenses.
You reduce the armor check penalty of armor you wear by 1 (to a minimum of 0) and increase the maximum Dexterity bonus allowed by your armor by 1.
When an ally adjacent to you is damaged by an attack, you can use your reaction to intercede. You take half the damage, and your ally takes the other half. This has no effect on spells, and any conditions delivered by the attack apply to both of you. In addition, you are now proficient with powered armor.
You can spend Resolve Points to ignore detrimental conditions. As a move action, you can spend 1 Resolve Point to suppress one of the following conditions for 10 minutes: exhausted, fatigued, frightened, nauseated, shaken, sickened, or staggered. After 10 minutes, if the condition's duration hasn't ended, the condition's effects return. You can suppress only one condition at a time; if you are both fatigued and shaken, you can avoid the effects of only one of them, and if you are affected by two different instances of the same condition, you're still affected by the second one.
You gain DR 3/-. At 17th level, this DR increases to 5/-.
As a standard action, you can set up a strong defense for yourself and an adjacent ally. Until the start of your next turn, you gain three benefits: your damage reduction increases to DR 10/-; you and the chosen ally each gain a +4 bonus to AC; and if you use guard's protection, you direct all the damage to yourself such that your ally takes none.