If intuition has to conform to the constitution of the objects, then I do not see how we can know anything of them a priori;
= approximately if our thoughts about objects have to come from objects themselves, we cannot them without experiencing the objects (here a priori is the opposite of "from experience."
but if the object (as an object of the senses) conforms to the constitution of our faculty of intuition, then I can very well represent this possibility to myself.
= If on the other hand, our "thoughts" about objects come from our thinking, then I can know something about objects without encountering them in the world.
Yet because I cannot stop with these intuitions, if they are to become cognitions, but must refer them as representations to something as their object and determine this object through them,
If I'm really going to "think" about objects, then I can take representations (= appearances) and get to objects
I can assume either that the concepts through which I bring about this determination also conform to the objects, and then I am once again in the same difficulty about how I could know anything about them a priori,
Here, I have a choice. I can either think the representations come from the things out there ... which will mean I cannot know them without experiencing those things.
or else I assume that the objects, or what is the same thing, the experience in which alone they can be cognized (as given objects) conforms to those concepts,
Or I can see the representations as matching my concepts.
in which case I immediately see an easier way out of the difficulty, since experience itself is a kind of cognition requiring the understanding, whose rule I have to presuppose in myself before any object is given to me, hence a priori, which rule is expressed in concepts a priori, to which all objects of experience must therefore necessarily conform, and with which they must agree.
And this works, because all of my experience follows a prior rules.
As for objects insofar as they are thought merely through reason, and necessarily at that, but that (at least as reason thinks them) cannot be given in experience at all - the attempt to think them (for they must be capable of being thought) will provide a splendid touchstone of what we assume as the altered method of our way of thinking, namely that we can cognize of things a priori only what we ourselves have put into them (Kant, Critique of Pure Reason, B xvii).
= the objects don't come from experience; they come from me thinking. So I can think about that sort of thinking and learn about objects and representations.
tl;dr - in Kant's view we don't have direct access to things in our world. Instead, we experience representations (whitish thing appearing in front of me) and objects (macbook air) based on categories and forms of sensibility that come from us.
Basic pattern = object -> representation -> thing. Object is something we can really think about. Representation is something we see/sense. Thing is something we don't encounter. (Again, his technical terms).
For Kant, a priori (non-experience-based) is the prize, because then we can have certainty. If we have to depend on encountering them, then he sees that as a problem (not explained in this passage).