Spellcraft and Spell-Like Abilities and the Like
When someone casts a spell, anybody who sees it can make a spellcraft check to identify which spell it is. The rules are unclear as to whether this also applies to spell-like abilities, which have no verbal, material, or somatic components.
So: you cannot use spellcraft to identify spell-like abilities, nor can you use it to identify spells which have no components, for example if they are cast with both silent spell and still spell metamagic and have no material components. You cannot even tell that the user is using a spell-like ability / casting a spell; if you're interacting with the user directly, such as being engaged in melee with them, you can tell that they are briefly distracted. During melee this allows you to get an attack of opportunity unless they cast defensively, as usual for spells. If someone succeeds at casting defensively with a spell-like ability or a spell which has no verbal, somatic, or material components, you do not even know that they are distracted; there's no evidence that they're doing anything, beyond whatever effects the spell or spell-like ability might produce. Note that you can only ready actions to trigger on things you can actually detect, so for example you can only ready an attack to trigger when someone uses a spell-like ability or casts a spell with no components if you are sufficiently engaged with them that you can tell when they're distracted. Threatening them in melee is sufficient for this. This type of trigger will also fail if they successfully cast defensively.
Spells cast with no components cannot be counterspelled. (Spell-like abilities cannot be counterspelled either, but that's already in the rules.)
You can still make the usual knowledge (arcana) check to identify the effects of the spell or spell-like ability once it is cast, and you can make the appropriate knowledge check for the creature type to identify which spell-like abilities a given creature has.