You're somewhere around Ops 10-15, and combat options are opening up faster than the game explains them. At Ops 10, your ships can fight other players' ships for the first time. At Ops 15, you unlock Station Combat -- the ability to attack other players' stations, and be attacked yourself. This is the basic map of what you're looking at and what you can safely tap on before either of those thresholds change how exposed you are.
In System view, every combat-relevant object is color- and shape-coded so you can tell what you're looking at before you tap it. Roaming hostile ships show up with red labels. Other players' ships are labelled in blue. Other players' stations sit near housing planets in systems that have them. Mission-related combat targets carry yellow labels with a mission marker on them. Swarm hostiles -- tougher groups of hostile ships -- also show red, same as regular hostiles, just stronger. Armadas use their own triangular icons in various colors; they can look like stations at a glance, but they're dangerous, alliance-scale threats that need real teamwork to take down, not something to tap into solo.
Tap any target in System view and a preview window opens, showing its type, strength, and an estimated difficulty rating -- exactly the kind of scan card you'd expect before committing a fleet. From there, SCAN pulls up more detail, and ATTACK sends your currently selected ship into the fight. The ATTACK button only appears at all if the target is actually valid for you to engage -- if you don't see it, something about the target (level gap, ownership, protection) is blocking the attack rather than the game glitching.
Before Ops 10, you're fully protected from ship-to-ship PvP -- you can't attack anyone and no one can attack you. Cross Ops 10 and that protection lifts: your ships become fair game whenever they're roaming or sitting idle in System view, though the game keeps matchups roughly fair by only letting players attack others whose Ops level is close to their own. Station vulnerability is a separate threshold: it only opens at Ops 15, when Station Combat itself unlocks. Until then, your station is untouchable regardless of your ship's PvP exposure.
Once Station Combat unlocks at Ops 15, tapping an enemy station launches an attack with your selected ship -- stations defend themselves with their own platforms plus any docked ships, and taking one down can require more than one pass. A successful attack triggers an automatic 10-minute Peace Shield on the defender, giving them a window to put up something longer. You can't attack stations belonging to your own Alliance's members. The mechanics of shields, Ceasefire, and what actually happens during a station fight get their own full breakdown in the Station Safety guide linked below.
Armadas are the one target type on this list you're not meant to solo -- they're built around coordinating with your Alliance, from picking a target together to timing simultaneous attacks. Trying to tap ATTACK on one alone is the fastest way to lose a fleet for no reward. The full rundown of Armada types, joining a strike, and what you actually get for participating is in the dedicated Armadas guides linked below.